bem

My Feedback: (1)

...to get what You dreamed about when You wasyoung.
When I was 14 years old (1975) I needed a new radio for the pattern planes I just started to dream about back then. I drooled over the ads and catalogs for Pro Line radio. I could not afford one in those days (a 7 channel Pro Line costed about US $400 with 4 servos etc at that time). So I had to settle for the less expensive EK logictrol super pro 7 ch radio, and it served well for many years (I still have it left). Today I use Futaba (14MZ). But the Pro Line dream never went to sleep. So when I some days ago happened to se one for sale I decided to buy it. This time it was cheaper - got it for US$240. Almost not used, had been stored in a box in a wardrobe in last 20 years. It is a Pro Line Competition Series 1975. I love it - even better quality then I had expected. The open gimbals are fantastic and inside the transmitter it is really neat and it "announce" very good quality (and still smell vinyl). Not hard to imagine why many top flyers prefered Pro Line back in the pattern hey days. I get some crazy idea that it could be worth to drop in a 2.4 GHz TXmodule in it. The radio is almost like new and maybe deserve to get into light flying duty again. A Mach 1 and this Pro Line would fit like a hand in a glove. Anyway, I took some pictures just to show this piece of old radio system history and also show what great radios we hadavailableback then. I also found some old ad for this 7 ch Pro Line radio in Model Airplane News from 1975 - it is fun to read. Even the original instruction manual was still together with my radio so I scanned it and maybe some of You are interested to read such old manual.
I scanned an original decal "Pro Line Equipped" that was still together with the radio just in case someone want one and maybe print a decal.
I finally arranged my radio like in the ad in MAN August 1975 and took a photo - kind of brings life to the old ad.

Next post: MANads and my "photo arrangement" to resemble one of the ads, and the Pro Line Competition series 1975 manual (PDF).

/Bo

bem

My Feedback: (1)

Pro Line Competition Series 1975 part 2

Manual: http://www.algonet.se/~boem/RC/Manua...975_Manual.pdf

/Bo

R_G

My Feedback: (1)

WOW!! Very nice find!

Looks like it's in mint condition! It would be a shame to "gut" it in favor of a 2.4 conversion! Is the 26.825 frequency legal to fly in Sweden these days? If so, I would leave it as it is. A very nice piece of R/C history there!

RG [8D]

dhal22

Very nice. Congratulations.

cllaurit

Nice find! I still have three of these somewhere around here. I used Pro-Line for years before switching to a Futaba 8JN (then later a JR unlimited 8).

TFF

The guy who taught me how to fly used Proline Competition and Kraft Signature. So I did the same thing, except I went with Signature. Hard to put down, isn't it.
Cool.

hook57

My Feedback: (21)

Great find Bem! I have two Pro-Line Comps and both are single sticks. Both are also modded to accept a 2.4 module and I can easily swap the 72 mHz deck back into it in few minutes (simple three pin Deans connector). Gotta love the feel of those gimbals!
hook

Taurus Flyer

Bem,

Never too late..., I hope I'm not!!!!



First to say, nice find,

I did design and built these kind of radio’s myself so I know any detail,(I am 10 years older than you are!).
I read maybe you want to transfer the radio to 2,4 GHz,

quote:
“I get some crazy idea that it could be worth to drop in a 2.4 GHz TX module in it.�

I recognize an old principle of encoder, “one shots� in the left bottom corner of the casing.
To show I did combine my picture (one shots 1/5) with yours.

Keep in mind, you only can use these encoders combined with the original old type/principle servo’s. It’s not a linear pulse width modulation system so the central position of modern servo’s will be disturbed.

The old servo’s are hard to combine with the modern receivers too , most of them did need a tap on the receiver battery (0 , 2.4 , 4.8V), so end solution can be you also have to exchange the encoder!

Important to think over and check my opinion before starting any modification c.q. , drill any hole, in your valuable radio transmitter.

Because my posts aren’t always visible in short time and often overlooked I also do pm you this important message.

Cees

bem

My Feedback: (1)

Ralph,

Yes it is still legal to use "27 MHz" band for RC (planes, cars, boats etc) here in Sweden. 26.825 Mhz has channel nr 86 today (and 7 other 27 MHz channelsare still in use here and legal to use). As long as You fly in places that are not near cities and villages where kids use their toy cars usually on 27 MHz it is not that dangerous to use 27 MHz here (except it is now as well back in 1970th the risk some crazy "radio amateur" start to send on high watts on 27 Mhz and "take down" everyting else that tries to communicate on that band).

If I would convert to 2.4 GHz it would be done by a professional RC repair company and I would make sure it was switchable between 2.4 GHz and original 27 MHz.

I have not investigated yet what companies may do such a conversion but I think Radio South in US do such work.

And I have not finally decided if I will do a conversion or just let it be as it is now.

As for battery replacement I do not know if LiFe (9,9 volt) TX pack would be possble to use in the Pro Line TX to replace the dead 9,6 volt NiCd pack that is in there today, but I will probably use NiMh batteries for both TX and RX so I get correct 9,6 volt for TX and 4.8 volt for RX.

By the way, anyone know what PLS model nr it isfor my servos (see pictures above)? I think it is PLS-11 servo because they have the servo wire exit underside the servo - I'm I right?
The Pro Line instruction manual mention:
PLS-1 (new for 1975)
PLS-3
PLS-12
PLS-11 (90 deg 0.52 sec, 2.10 Kp)
PLS-14
PLS-15 (90 deg 0.56 sec, 2.38 Kp)
It was also a PLS 180 deg servo (retract servo, 2.5 sec, 2.85 Kp)

I looked in two old Swedish hobby catalogs from the company that sold Pro Line herein Sweden back then, "Essen-Air" and in 1977 cataloga Pro Line 7 chwas delivered with PLS-11 or PLS-15 servos as standard. The 5 ch Pro Line Challenger II was delivered with PLS-11 servos as standard according to the catalog.
It is funny to read these old catalogs - they sure wanted to present Pro Line as "the best" radio (and it probably was at that time) - they write in Essen-Air 1977 catalog:

"They [Pro Line] have been imitated but never duplicated."

"Rolls-Royce among RC systems. Constructed and made in USA"

"Of the 32 competititors at selection for 1973 World Championshipat Huntsville Alabama 19 used Pro Line. The selected WC team Jim Whitley, Norm Page and Jim Martin used of course Pro Line. These elite flyers did not pick a radio in the stack."

"Delivered with military spec. potetiometers with 1% liniarity with lifespan of 25 000 000 operations." (that was optional in 1975 but standard in 1977 it seems).

Picture below from the Swedish Essen-Air catalog 1977 showing the company owner Mr Essen Ek (top picture) with a Pro Line Competition Series with his F3A pattern plane "Sly-Bird" (a rather common F3A plane in beginning-middle 1970th here). Second picture is another RC entusiast also using Pro Line and he has a Sly-Bird also.

I would love to see an originalPro Line catalog from this time period - anyone that has one?


/Bo

bem

My Feedback: (1)

Cees

So if I will continue to use this Pro Line radio with the original 27 MHz encoder must I always use Pro Line servos?

I opened the old original Pro Line 500 mAh battery receiver pack and it has a circuit board in it - do You know what is it for?
So when I want to get new batteries (and if I will use it as original 27 MHz system) with orginal servos I must make sure this circuit board is used in the new battery pack again?

I will open the TXcase later and check if the TXbattery has some special circuit board also in it.

/Bo

doxilia

My Feedback: (3)

Bo,

beautiful Pro-Line! It does appear as if it has never been used too.

The beauty of it is that it is actually a "modern" radio. By this I mean that unlike the earlier 70's radios that used three voltage levels (0, 2.4 and 4.8V), this one is a two voltage level radio (0 & 4.8V). At least the older Kraft's used the three voltage levels along with 4 pin connectors to carry the ground (0V), center (2.4V), full (4.8V) and signal (typically an orange or yellow wire but in Tx's different colour wires were used for each channel signal) connections. As we can see your Pro-Line is a modern three pin system. (Cees was suggesting that it might be a four pin system but it is clear that it isn't.)

As such , your Tx should be compatible with any equivalent pulse system provided they are on the same band. I can't recall if Pro-Line were negative or positive pulse but I believe the latter (I'll have to check). If memory serves, Futaba and HiTec are negative pulse systems while JR, Spektrum and Airtronics are positive pulse systems. I used to have this stuff at my finger tips a year ago but I have been thinking about paint lately instead . In any case, if Pro-Line is positive pulse, with the installation of a compatible RF deck, you could use the Tx with any modern Rx of the same type (e.g., Spektrum 2.4 GHz deck). This of course goes for FM too. A JR FM deck could then have the Tx operate on say the 72 MHz band with a JR FM Rx such the common 600 and 700 series Rx's.

It was/is very common to modify Ace MicroPro 8000 systems (arguably a superset radio to the Pro-Line's and Kraft's) that were originally on the 27 MHz AM band to operate on the 72 MHz FM band or the 2.4 GHz FHSS (e.g., Futaba FASST). The Ace systems were negative pulse systems so they are compatible with Futaba and HiTec systems although Ace at some point also introduced a pulse inverter into their system allowing it to be used on either system. The Ace systems were also "modular" so the switch between AM and FM was a simple matter of swapping out one RF deck for another and attaching two connectors: one to the encoder (a three pin connector) and one to the antenna (a single lead three pin connector). Deans micro connectors were used on these connections. The modules were attached to the back of the Tx case with two screws much like the way your deck is attached to the top of the case front. Later, people just used industrial velcro to secure both the flat battery pack and the RF deck.

Your Pro-Line is also modular in the sense that the RF deck is not built into the encoder - nice! The deck is the circuitry in the upper left of the Tx when seen from behind. It is held on by two screws from the top of the Tx beside the "slow roll" switch. If you would like to make your Pro-Line "fully" modular what would be required is to install a module switch that would select between the different modules present in the Tx. Modern day third party 2.4 Ghz decks are very small and look a bit like a BEC or ESC if you will. They are typically shrink wrapped in plastic and have two connectors on them, one for the encoder and one for the antenna - that simple. The battery is likely velcroed or screwed to the back of the Tx case. This is a good spot to also install the 2.4 Ghz deck - probably above the battery in the center of the case plate so that it nestles between the gimbals behind the power switch. A little soldering work would be required to re-route the encoder wires from the current AM deck to the module switch. The encoder connector on the 2.4 deck would also be soldered to the module switch in such a fashion that when the switch is in one position, the AM deck is powered and connected to the encoder, when the switch is in the other position, the 2.4 deck would be active.

Because such a switch is crucial to the Tx's broadcast, flipping the switch accidentally would effectively turn off the link between Tx and Rx. It is therefore a good idea to use a locking pull switch for such application. You effectively have to pull and flip the switch to change bands. Other than that though, you should be able to operate the Tx without having to change modules, open the Tx or otherwise fiddle with the interiors on and off depending on what Rx/Model you want to fly. Of course, if you want to have both AM/FM and FHSS bands available you will need to also install a 2.4 GHz antenna somewhere on the top of the Tx. It should be quite doable.

Coming back to the battery quickly, you could use any battery chemistry you like regardless of nominal voltage in the 9-12V range. One caveat, you could use a LiFe or a LiPo 3s type battery but at least with the LiPo it would be a good idea (while perhaps not necessary - that depends on the encoder voltage regulator) to also route the power through a voltage regulator (e.g., CC BEC) to the encoder. Modern encoders including your Pro-Line have voltage regulators built into the encoder to knock the voltage down to something like 5V (usually for the transistors and/or IC's). If they are designed to operate with an 8s NiCd pack (as it probably was), then the voltage variability in a NiCd pack (between full and empty charge say) is also within the variability of the LiFe pack. As such, there should be no need to regulate the power coming from a 3s Tx LiFe pack just like there is no need to regulate a 2s LiFe pack with modern Rx's and servos. I have run some 4.8V servos (i.e., not 6 or 7.2V servos) with 2s A123 packs without issue although it does arguably shorten the lifespan of those particular servos. With that said, using a voltage regulator in both Tx and Rx's is a good idea anyway as feeding a constant power to circuits and servos results subjectively in more "linear" performance. I do prefer to use 6V regulators now whenever using A123 2s airborne packs and the servos "appreciate" it...

A Mach 1 along with this radio would indeed make a nice setup!

Congratulations on your find Bo,

David.

Taurus Flyer

Bo,


The encoder translates the position of the potentiometers of the sticks in a pulse train, circuit board left side bottom position in the casing.
Started by the a-stabile multi vibrator any 20 msec, there is a kind of controlled demolition of the “one shots� . First the aileron, next throttle, elevator, etc. The pulses are visible in the carrier wave of the transmitter by short interrupts of about 50 uS.

Servo’s do translate these pulse length, after been distributed by the decoder in the receiver, in a related position, examples of the “modern�relationship: pulse length 1 ms, 0.5 ms and 2 msec in resp. 0%, 50% and 100% position, but of course also any position between these reverence values.

The “old� encoders, of which I think yours is one of, also do have 1 and 2 ms for respectively 0 and 100 % BUT about 1.4 or maybe 1.3 ms for 50 % position.
These modulation relationship is result of a-linearity of the one shots system and compensated by the one shot (monostabile multi vibrator) in the servo. When you use modern servo’s the central position of the stick isn’t the central position of the servo anymore because the a-linearity isn’t compensated anymore.

So it hasn’t to do with the 27 Mc but with the translation key between transmitter pulse length and servo positions. So if you transform the transmitter to 2.4 GHz you still can use original servo’s and the system will probably work as you want with the original servo’s but not with modern servos.

The old type of servo’s without the battery tap on 2.4 V (so three wire) also were there in the past, for example Microprop, and already in the period of these a-linear encoders. So I do not know if there were 3 wire servos for this radio.

Let it be clear it’s my opinion and it is what I see and recognize, that encoder cannot by linear as needed for modern (analog or digital!) servos.

Hope it is clear, if not, please ask, difficult language. About the battery pack I will write my response this evening if not anybody else of the country of origin knows .

Cees

doxilia

My Feedback: (3)

Bo,

some comments in line blow.

David.

Note that the encoder and the RF deck are separate entities. There is no such thing as a "27 MHz encoder". The encoder does the signal encoding from the gimbals and switches and transfers these channel modulations (voltage variations if you will) over to the frequency (RF) deck. In this case, the 27 MHz AM deck, then relays a voltage variation over a baseband signal (a specific frequency in the 27 MHz band) to the Rx which has a comparable RF deck which relays the signals over to the Rx decoder. Those decoded signals in turn are directed to the appropriate channel feeding the servo a voltage pulse within a given maximum pulse width. So the voltage pulse dictates how much the servo should move from center on one direction or the other. A little crude but in a nutshell that's how it works.

The circuit board in the Rx battery back is likely also a voltage regulator - I see a bunch of diodes ([8D]). It is probably designed to work in tandem with the battery charger which is a little more simplistic than chargers today which rely on programmable IC's. It might also serve to deliver a constant nominal output. In order to test this, you could remove the circuit from the pack and attach the two leads from the original batteries going to it to a fresh 4.8V pack that you know is working and charged. With a voltmeter you can then measure what's coming out the other end of the circuit (no point in one unless there is an in and an out ). Knowing this voltage will tell you what the Rx is expecting to see but I suspect that the circuit has more to do with the limitations of the NiCd chemistry of the day than it does with the electronics inside the Rx. But I might be wrong.

The important thing to keep in mind about batteries is to make sure they are delivering the correct voltage to your system. You don't have to use that particular circuit but if it is indeed a voltage regulator that feeds the Rx a constant voltage, why not! Take it out of the pack, route the input and output leads to some connectors and shrink wrap the little fellow with plastic tubing. You can then connect this inline with the Rx after the radio switch so that when you charge your modern battery pack, you bypass the regulator (modern chargers are smart today so they know how to charge modern chemistry batteries properly).

Of course, if you use a modern 2.4 GHz Rx and servos that voltage regulator may not be suitable. It might be set to output 4.8V which would in general be too low for typical 2.4 GHz positive pulse Rx's such as JR/Spektrum. (We have to confirm that the Pro-Line is indeed a positive pulse system. If it's not, then one can substitude the word negative wherever I said positive and Futaba wherever I said JR )

If it does, it probably serves the same purpose. Check it's output but again I suspect it has more to do with the chemistry quality of NiCd's back in the day.

The beauty of these radios really resides in the Tx and their gimbals. It is hard to deny the reliability and improved performance obtained from all other modern day components starting from the Tx RF deck forward. In the following decremental order, these are the components that I would typically prefer not to use from vintage (classic) radio systems:
[ul][*] Batteries[*] Rx Switch[*] Servos[*] Rx[*] Tx RF Deck[*] Tx Encoder[*] Tx Switches[*] Tx Case[*] Tx Gimbal Pots[*] Tx Gimbals
[/ul]
Looked at another way, in reverse order, the items above are the ones I consider worth salvaging in putting a vintage radio back into service. If you can't salvage the gimbals, it's probably not worth doing.

David.

doxilia

My Feedback: (3)

Bo,

by the way, was this a Swedish bought radio? Do you know what the SVART/VIT means on the printed label beside the 26.825 frequency below the power switch?

David.

cllaurit

I remember when ACE bought the remainder of Pro-Line. I lusted after the Silver Seven and when they came out with the white case it was a done deal. Built from the kit and I still have it today.

Many many years ago I met Jim Fosgate at CES (Consumer Electronics Show) in Las Vegas, he was there promoting Rockford-Fosgate audio equipment. As corny as it was I thanked him for making the best damn radios you could buy. Funny thing is no one around us knew what the hell I was talking about.

doxilia

My Feedback: (3)

Good story!

Is you white case radio an Ace 7 channel or a MP8K?

David.

cllaurit

I have both but the Silver Seven is a white case as is the MP8K

NM2K

My Feedback: (14)

I longed for, but never obtained, a Pro Line Comp or Kraft Signature radios. I built and flew a ton of the Ace Commander series kit radios and more Bantam Midget servos than I care to remember. They worked flawlessly, I might add.

My only "revenge" for not owning the two top of the line American R/C systems was my cheering at the news that Allen-Bradley, the manufacturer of those super smooth mylar element stick pots, had stopped producing said pots. As though any original pot of such description would actually ever wear out.

Ah, the good old days...<G>


Ed Cregger

bem

My Feedback: (1)

David,

That was much valuable information. Thanks.
If I do the conversion to 2.4 GHz (and switchable between27 MHz and new 2.4 Ghz) I will let a RC repair company do this. I doubt any here in Sweden will do it so it will probably be shipped overseasmaybe to Radio South in US. They have info on their homepage that they do conversions to 2.4 GHz of Pro Line and other brands.

I just opened the TX case for inspection of the TXbattery. I see no circuit board similar as it is in the RX battery box. So it is probably just the 8 cellNiCd TX battery (500 mAh)- it is two black, one yellow and one red wire thatexit the battery and goes straight to the on/offswitch forthetransmitter.

However when Ichecked the circuit board above the battery pack Idiscovered that it was a "green"substance probably from the old NiCd battery leaking some. I cleaned the circuit board with a hard paint brush and water (to solve the green substance little easier) and I managed after an hour or so of cleaning with help of a magnifying glass remove most of the green stuff.
I also noted that to the right it was one lead on the circuit board that had a break. Easy to repair (I could do it myself but I will let the RC repair man fix it when I send it in for service and new battery pack and possibly 2.4 GHz conversion. What do Youthink guys - is that board clean enough? After repair of the broken lead it should be sprayed with circuit board protection lacquer again.

While I hade the TX case open I checked the potentiometer type and it was marked as below. I suppose it is not the "Optional transmitter potentiometer conductive plastic control pots with 1% liniarity" that Pro Linementioned in the Model Airplane Newsad above.
The gimbal pots in my TXis marked:
AB
96829A
U-5K-OHM
TYPE J


Yes my Pro Line was bough here in Sweden, from Essen-Air probably since this companywas as far as I know the importer here and only reseller of Pro Line radio at that time (1975) here in Sweden.
The label with the frequency 26.825 and "SVART/VIT" on my Pro Line is like this: Here in Sweden we had color frequency flags on 27 MHz band, one color for each approved frequency.
The color was black/white (svart/vit in Swedish) for frequency 26.825. This frequency color system was changed to numbers later (when 35 and 40 MHz was approved in our country) so all approved frequency in 27 MHz band had numbers and all 27 MHzclothespin was marked with the ch number and color for all of them was and still is brown and You must have the clothespin on the TX antenna before You are allowed to switch on the transmitter of course at the flying field.

/Bo

Taurus Flyer

Bo, because I was curious.

With the use of your pictures it was possible to reconstruct the electronic circuit diagram of an key part of the encoder, some “one shots�.
Conclusion, it is exactly the same diagram I did use in the past myself. My source was Simprop, the German brand.

If you want to know the pulse lengths at 0 – 50 – 100 % position of the stcks, an electronics engineer in Sweden can show them on a CRT, see the orange triangles.

Also visible for example, needle pulses of the train to trigger the modulation of the carrier wave, red dot.
It isn’t interesting in this thread to explain more, only one important fact to know, the simplicity of the diagram combined with the principle and selecting of components in transmitter and servos was the key for stabilty related to temp. stability/voltage so the accuracy of the total system.Only an simple zener diode stabilizer was enough for this encoder for example.

About the stick potentiometers I read:

I suppose it is not the "Optional transmitter potentiometer conductive plastic control pots with 1% linearity" that Pro Line mentioned in the Model Airplane News ad above.

IMO these are Allen Bradley high quality pots, much better for example than the Bourns 3851A-282-502BL (10/20 % total resistance tolerance and 10 % independent linearity !!) of which I did read some time ago as where combined with modern digital encoders. My advice would be, never exchange them unless there is one defective. See my own transmitter picture, my gimbals are worthless without the original wirewound potentiometers.

If you want information about the batteries, send me a PM, but I think any company that will do modifications for you can tell you the details.

Good luck with your radio and thanks for the information.
Cees

R_G

My Feedback: (1)

Bo,

This thread might be of some interest: [link=http://www.rcuniverse.com/forum/m_4645808/anchors_4645808/mpage_1/key_/anchor/tm.htm#4645808]http://www.rcuniverse.com/forum/m_4645808/anchors_4645808/mpage_1/key_/anchor/tm.htm#4645808[/link].

The last post mentions [link=http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=bourns+6639&x=19&y=22]www.digikey.com[/link] as a source for possible replacement pots if you need them.

RG

doxilia

My Feedback: (3)

Bo,

Ralph's thread pointer was helpful in that it clarifies that those are Allen-Bradley pots, at least on the main gimbals which I assume is the subject of the photo. Like many American made radio's, 5 kOhm pots are used (on single stick Tx's one would occasionally see 10 kOhm pots on the rudder knob but rarely) and they are typically used from off to x% meaning that the voltage is controlled by allowing current to flow from 0 to a certain percentage of maximum resistance. In other words, the pot is never fully thrown from one end to the other. In order to accomplish this, the stick or trim are limited mechanically by either the gimbal opening or the case cutout on the trim levers. Note that this is different from most current Japanese designed radio's which typically use and deflect the pot left or right from 50% (i.e., center pot).

In any case, all this might be information which you might not need or want... If Tony at Radio South will be doing the check on the radio, he can verify whether the pots are still clean and functioning properly. It is likely that one won't be able to source the same AB pots but there are several good replacements not the least of which would be Spectrol pots - expensive but very high quality. Many Kraft and Ace radio's used less expensive but still good Bourns pots.

David.

doxilia

My Feedback: (3)

Glad to be of assistance.

Tony at RS is evidently a very competent RC technician - I wouldn't hesitate to send him a radio. However, my understanding is that their conversions are fairly standard using a "modular" system which allows plug-in modules to be inserted into the radio. Mark (hook) made a comment about this as he has a couple (or more) of radio's done this way from Tony. If I were you, I would ask him to make the conversion so that it is "selectable" but not "swappable" meaning that you want to have two (or three: AM, FM, FHSS) RF modules in the system that are selected via the switch discussed above but doesn't require you to physically exchange one module for another in a module receptacle.

Personally, I'd be very weary of using a radio on AM these days. Not only for direct interference reasons with other land based RC systems but also because of the much more "radio contaminated" environment we have compared to 30-40 years ago. I wouldn't be surprised if Radio South had a number of suitable Pro-Line FM RF decks that could be replaced for the AM deck. If the radio was mine (which it clearly ins't), I would have it converted to both FM PPL and FHSS/DSMX (2.4). This would allow it to be used with a wide variety of modern, reliable 72 and 2.4 receivers. Frankly, putting a 30-40 year old Rx (with brittle solder joints) in a model which vibrates is a risky proposition at best. Having said that, if Tony gives it the green light, why not. When you think about it, the beauty of these analog radios is in the gimbals and the simplicity and robustness of the Tx case. As far as Rx's and servos go, well, that's another story. But, using a 30-40 year old flight pack would certainly make a classic model of the same vintage a true re-creation.

Good. It's possible that the voltage regulator in the encoder portion of the Tx takes care of proper voltage whereas the Rx might have not been "big enough" in those days to have the regulator built on to the Rx circuit. As simple as it may be, that battery voltage regulator is rather large. As for the wires, I believe your radio has a trainer function that may be connected via the same connector on the rear right of the Tx used for charging the battery. It looks like a 5 pin (minimum) DIN connector. The black wires from the battery are likely the ground (or negative) wires with the red and yellow being positive voltage wires. The red might deliver the full voltage level to the switch/encoder while the yellow might be a knocked down voltage level (taken care of by the voltage regulator) to deliver some lower level voltage to the trainer function at the DIN connector. You can check to see if there is a yellow wire going to the DIN connector. Another possibility is that the yellow wire powers the encoder with a lower level voltage (e.g., center tap 4.8V) while the red one, at full voltage (9.6V), might be needed for the RF deck for full broadcast power. But this is just an idea. You'd have to follow the leads to see what's going on.

That is the kind of thing that could happen inside the Rx and servos with aged joints and brittle solder.

If Tony deems that the encoder is still salvageable (it's not just the solder joints but capacitors can vent, resistors can become brittle, silicone can break down, etc.) then so be it. Otherwise, I think you'll have a perfect radio candidate for conversion to a very nice encoder design based on the Ace MP8K, the Micro Star 2000 (MS2K). The encoder is a marvel of functionality and will convert your good quality Pro-Line gimbals into a whiz bang modern radio. The only drawback of the MS2K encoder is that it is a "do it yourself" encoder designed to be built by the end user. There are builders that you can hire to build the encoder and generally convert your radio from the bottom up to an excellent quality computerized modern system. If none other, one of the nice things about the MS2K encoder is that it has memories for multiple models so it allows the tx to be used on several planes rather than being relegated to a single (well, maybe two; one per RF module) Rx/model setup. Things like trim positions can be electronically stored so that each model has the proper settings. Basically similar to modern day Tx's but with a vintage feel. Although that is a single stick Pro-Line, The Tx pictures in the link below give you an idea of what I'm talking about:

http://www.mstar2k.com/index.php?opt...ures&Itemid=53

You might also want to poke around the www.mstar2k.com website in general. There are many radio conversions shown in the various pages.

Makes perfect sense. That's how it is here too.

David.

pimmnz

Bem, given you said that there was a green gunge on the circuit board with the break in the copper land it would seem that the cells have leaked electrolyte through the negative battery lead. I would be concerned that this circuit is now U/S and the radio probably unrepairable.
Evan, WB #12.

Wayne Miller

Hi,

Regarding the printed circuit board and the diodes in the battery pack. Typically back then you would wire diodes into the battery pack as a "fail safe". If a NiCd went bad while flying, it would become a resistor. The Diodes were designed to by pass a bad battery and still have enough power to the receiver and servos so you could get the plane home. The servos would work slower, but they would allow you to land.

Attached is a PDF of the wiring and explaination. If you used servos with a third wire as a 2.4v center tap, there would be another wire in the battery pack from the center of the pack to the battery pack connector.

I hope you find this useful.

Fly4Fun,

Wayne