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KC9OXP
09-04-2009, 02:45 PM
I am trying to build a 2 meter amp with a salvaged radio. It is an old train radio so I know They will bump down to 2 meters. Now what I don't know if is it ran on FM or AM.

If it is an AM radio will the transistors still work for FM of same frequencies?

Does any one by chance have a schematic or data sheet for-
M9622, M9623, M9624, M9625?
Don't waste your time Google those, their is nothing, but web sites in china that says they will sell them to me, but they seem to be fake sites, you can type a fake number and it will pop up they have it in stock.

I am currently trying to reverse engineer the board, the way it is set up now I can not trigger them. I think the circuit is just to well tuned. I can how ever remove a capacitor and strike it with RF and get a very strong oscillation so i know they are still good.

The transistors I am trying to use have four leads. They are probably from the late 60's to upper 70's judging by the way the radio looks.

AD2U
09-04-2009, 02:50 PM
They will work equally well in either AM or FM.

You can google Motorola GM300 schmetics and read the RF final amplifier circuit as a starting ponit.

KC9OXP
09-04-2009, 03:01 PM
Ok thank you, I found the schematic real easily, once I get done back tracing the old amp circuit, i think i can figure out the orientation of the transistors.

What is the typical configuration of a 4 lead RF amp transistor shaped like a plus sign with an aspirin sitting in the middle?
...............
...... #.........
...... #...........
. ##(M)##.......
...... #............
...... #...........
.................

AD2U
09-04-2009, 03:16 PM
What is the typical configuration of a 4 lead RF amp transistor shaped like a plus sign with an aspirin sitting in the middle?


Two of them are shorted out - they are emitters
The one with a cut at the corner will be the collector

KC9OXP
09-04-2009, 03:21 PM
I think i will have to desolder one to see if the lead is nicked, they have a dot at the top on the ceramic could that be the collector, as far as i can tell their no leads are shorted they have capacitors it appears bridging 2 exempt for 1 that has a tiny coil bridging 2 leads and that one has no dot.

AC0FP
09-04-2009, 03:34 PM
I think i will have to desolder one to see if the lead is nicked, they have a dot at the top on the ceramic could that be the collector, as far as i can tell their no leads are shorted they have capacitors it appears bridging 2 exempt for 1 that has a tiny coil bridging 2 leads and that one has no dot.

A dot on the type of transistor your talking about often indicates the collector. What brand of radio are you working on?

73,
:)

KC9OXP
09-04-2009, 03:39 PM
Ya after i removed it from the board their was a corner nicked on the lead with the dot. It is an old Motorola Micor T42K. I tried making a head unit for it but never did find the right schematic for it so it never worked. So I am just gonna pull the parts from it and use it to make a amp so I can push more then 5 watts around here.

WB3BEL
09-04-2009, 03:45 PM
An easier way than unsoldering in a common emitter RF power amplifier which is probably what this circuit uses is look at two leads that oppose each other they are likely soldered to ground traces. You can see this pretty easily as large copper area peppered with via holes. Or use your ohmmeter to check that the copper area you suspect is ground is connected to the chassis. This is not always true but very often so in negative ground radio systems. It's usually obvious by inspection.

If the radio is meant to operate from 12V you can determine which RF amp transistor lead is collector by measuring the voltages. It will likely be the transistor lead with highest voltage to ground nearly 12V when the circuit is energized.

The base will have lower voltage. If class C with no drive it will have zero volts. If AB biased it will have 0.5 to 1V.

Color Dots on RF power transistors may indicate lead orientation but often they indicate transistors have similar DC bias matching.

K7JEM
09-04-2009, 03:51 PM
Those are PNP transistors, so they're a little harder to work with in 12v negative ground applications.

IIRC, the 22 is about .4 watts in, and 4 out, the 23 is about 15-20 watts out, the 24 is about 35 and the 25 is about 60 watts out. They are not real high gain transistors, these are from the early 70's.

The 23 or 24 would probably make a pretty good amp for 5 watts in. The problem will be the design, and whether it's worth it.

Joe

AI3V
09-04-2009, 04:01 PM
I am trying to build a 2 meter amp with a salvaged radio. It is an old train radio so I know They will bump down to 2 meters. Now what I don't know if is it ran on FM or AM.

If it is an AM radio will the transistors still work for FM of same frequencies?

Does any one by chance have a schematic or data sheet for-
M9622, M9623, M9624, M9625?
Don't waste your time Google those, their is nothing, but web sites in china that says they will sell them to me, but they seem to be fake sites, you can type a fake number and it will pop up they have it in stock.

I am currently trying to reverse engineer the board, the way it is set up now I can not trigger them. I think the circuit is just to well tuned. I can how ever remove a capacitor and strike it with RF and get a very strong oscillation so i know they are still good.

The transistors I am trying to use have four leads. They are probably from the late 60's to upper 70's judging by the way the radio looks.


They will work equally well in either AM or FM.

You can google Motorola GM300 schmetics and read the RF final amplifier circuit as a starting ponit.


Be careful here.

If the original set was FM (class C), the transistors may not be suitable for Linear (AM/SSB/PSK) service(class AB)

Follow WB3BEL's advice about the base voltage, and if it's biased for class C, it's best to do a 3rd order intermod test if you re-bias for linear service.

Rege

AD2U
09-04-2009, 04:07 PM
Those are PNP transistors, so they're a little harder to work with in 12v negative ground applications.


Never heard of PNP VHF RF power transistors before, especially for a design from 70s.

In a PNP transistor, the majority current carriers in emitter and collector regions are holes, which are much more difficult to move around.

AD2U
09-04-2009, 04:10 PM
Be careful here.

If the original set was FM (class C), the transistors may not be suitable for Linear (AM/SSB/PSK) service(class AB)



He most likely will use the AMP for FM work around 2M.

If the original design was for AM, then the transistors should also work well in a class-C FM circuit.

K7JEM
09-04-2009, 04:16 PM
Never heard of PNP VHF RF power transistors before, especially for a design from 70s.


Nevertheless, that's what they are.

I changed out lots of those in Micors in the late 70's and early 80's.

Joe

KC9OXP
09-04-2009, 04:20 PM
Ok, I found a stamp on the radio, it was FM. The Xtals show it ran on 160 through 161.6 MHz.

The stepping makes sense, the amping circuit was feed directly from the Xtals (PLL?).

Class C, I will have to do some research i have only built Class A's and AB's.

As far as I can foresee this amp will just be for FM.

So if this is a bias transistors, I will have to build a voltage divieder, then inject the 5 watts onto it? I have 2 levels on the hand held "1\4 W' and "5 W."

The photo attached is a preliminary trace of the one I have started from.

KC9OXP
09-04-2009, 04:27 PM
Found a class c schematic http://sss-mag.com/pdf/classc.pdf .
Looks like if I get this going I am going to have fun with the coils from the radio to tune it so I can use it legally. At least the coils for the input are close and I think i can get the outputs in tune by adding half an inch of wire and retuning the coils.

K7JEM
09-04-2009, 04:28 PM
Ok, I found a stamp on the radio, it was FM. The Xtals show it ran on 160 through 161.6 MHz.

The stepping makes sense, the amping circuit was feed directly from the Xtals (PLL?).

Class C, I will have to do some research i have only built Class A's and AB's.

As far as I can foresee this amp will just be for FM.

So if this is a bias transistors, I will have to build a voltage divieder, then inject the 5 watts onto it? I have 2 levels on the hand held "1\4 W' and "5 W."

The photo attached is a preliminary trace of the one I have started from.

Yes, those were FM. The exciter put out .4 watts, and the PA board amplified that up to 45-110 watts, depending on which amp you had.

It is not a simple matter to build an amp out of one of these things. You would be better off using another type of transistor. The original design from Motorola had enough issues, and they spent tons of money engineering that puppy.

Just the fact that these are PNP presents special issues. The fact that they are 35 years old presents others. RF transistors were in their infancy back then, and have been improved upon a lot through the years.

Joe

KC9OXP
09-04-2009, 04:38 PM
Yes, those were FM. The exciter put out .4 watts, and the PA board amplified that up to 45-110 watts, depending on which amp you had.

It is not a simple matter to build an amp out of one of these things. You would be better off using another type of transistor. The original design from Motorola had enough issues, and they spent tons of money engineering that puppy.

Just the fact that these are PNP presents special issues. The fact that they are 35 years old presents others. RF transistors were in their infancy back then, and have been improved upon a lot through the years.

Joe

I am too broke to get any other transistors, so I just try to build what I need for now. I believe that radio was set for 65W. What kind of specialty is it needing with them being PNP? Is it just keeping the amp transistors ground Isolated from the power supply ground?

K7JEM
09-04-2009, 04:51 PM
I am too broke to get any other transistors, so I just try to build what I need for now. I believe that radio was set for 65W. What kind of specialty is it needing with them being PNP? Is it just keeping the amp transistors ground Isolated from the power supply ground?

Those transistors are designed to work on a good double sided copper clad board. They need ample ground pads on the emitters, but those ground pads will be at +12v. Unless you know what you are doing, this will not turn out well.

You could probably take a schematic from a 2N6082 type transistor and use it for a starting point. Then reverse all of the voltages. Then change out some of the parts.

Joe

AD2U
09-04-2009, 05:14 PM
Nevertheless, that's what they are.

I changed out lots of those in Micors in the late 70's and early 80's.

Joe

Care to offer a lead to PNP VHF power transistors' datasheet or model number?

KA4DPO
09-04-2009, 05:21 PM
You will need to float the amp and also make sure that if you're using a broadband transformer at the output that the output winding is isolated from the input side. You don't want +12 volts on the shell of the PL-259. I don't think it's particularly hard as long as you keep the ground side of the amp well isolated. If you plan to use a heatsink you can insulate that as well so there's no electrical contact with the the chassis.

AD2U
09-04-2009, 05:24 PM
Care to offer a lead to PNP VHF power transistors' datasheet or model number?

Never mind, I find the schematics

http://www.repeater-builder.com/micor/pdf/micor-132-174-mhz-service-sheet-pg2.pdf

This site has a lot of info on that radio

http://www.repeater-builder.com/rbtip/micor-index.html

AF6LJ
09-04-2009, 05:27 PM
Yes, those were FM. The exciter put out .4 watts, and the PA board amplified that up to 45-110 watts, depending on which amp you had.

It is not a simple matter to build an amp out of one of these things. You would be better off using another type of transistor. The original design from Motorola had enough issues, and they spent tons of money engineering that puppy.

Just the fact that these are PNP presents special issues. The fact that they are 35 years old presents others. RF transistors were in their infancy back then, and have been improved upon a lot through the years.

Joe
Having worked on a few myself, this is good advice to heed.

KC9OXP
09-04-2009, 05:28 PM
I am looking for a schematic that uses those, I take it the order of the pins should probably be the same?

Good luck findings a datasheet for the ones I have.

I should have no problem floating the amp, the isolation on the output may be a trick for me.

Do these need to be biased? Or just inject the RF into base?

AD2U
09-04-2009, 05:32 PM
I am looking for a schematic that uses those, I take it the order of the pins should probably be the same?

Good luck findings a datasheet for the ones I have.

I should have no problem floating the amp, the isolation on the output may be a trick for me.

Do these need to be biased? Or just inject the RF into base?

THis site has every thing you need to know and more

http://www.repeater-builder.com/rbtip/micor-index.html

K7JEM
09-04-2009, 05:33 PM
Never mind, I find the schematics



So, do you think they are PNP or NPN?

KC9OXP
09-04-2009, 05:34 PM
Never mind, I find the schematics

http://www.repeater-builder.com/micor/pdf/micor-132-174-mhz-service-sheet-pg2.pdf

This site has a lot of info on that radio

http://www.repeater-builder.com/rbtip/micor-index.html


Man I have been looking all over for that schematic, no one had it! I am even in the yahoo group for it.

AD2U
09-04-2009, 05:37 PM
So, do you think they are PNP or NPN?

PNP for the finals and NPN for the exciter.

K7JEM
09-04-2009, 05:43 PM
PNP for the finals and NPN for the exciter.

Right. But the part numbers he is talking about are all in the PA.

You need to understand that there are many people here that have worked on VHF Micor radios, and are experts on them. They were the Motorola flagship product during the 70's and early 80's. I probably worked on hundreds of those things. There are still a lot in ham repeater service. Our club pulled our last one out just a couple of years ago.

Joe

AD2U
09-04-2009, 05:52 PM
Right. But the part numbers he is talking about are all in the PA.

You need to understand that there are many people here that have worked on VHF Micor radios, and are experts on them. They were the Motorola flagship product during the 70's and early 80's. I probably worked on hundreds of those things. There are still a lot in ham repeater service. Our club pulled our last one out just a couple of years ago.

Joe

Never thought of creating a PNP RF power transistor for VHF band. On paper, a NPN type will be more efficient. There must be something else that was more important than efficiency, like stability or thermal consideration. It would be very interesting to find guys that designed these transistors.

AD2U
09-04-2009, 05:57 PM
Man I have been looking all over for that schematic, no one had it! I am even in the yahoo group for it.

Now you have something to do for the long weekend.

K7JEM
09-04-2009, 06:16 PM
IIRC, the M9624 is equivalent to a 2N6096. There are regular part numbers for most of those Motorola parts.

I think the 9622 is a 2N6094, the 9623 is a 6095, the 9624 is a 6096 and the 9625 is a 6097. They are pretty much obsolete now, and very expensive if you can find them. AFAIK, they were only used in Motorola equipment.

Joe

KC9OXP
09-04-2009, 06:29 PM
I wounder why I can not get this thing to trigger. I have bypassed the first transistor and plugged into where the 4 watts would out put. So that eliminates the current limiter.
It would appear that mine is the 45 watt class, the only difference in the board number is their is a 7 on the end.

AD2U
09-04-2009, 06:47 PM
I wounder why I can not get this thing to trigger. I have bypassed the first transistor and plugged into where the 4 watts would out put. So that eliminates the current limiter.
It would appear that mine is the 45 watt class, the only difference in the board number is their is a 7 on the end.

If I were you, I would disconnect Q501's collector and use a resistor ladder to feed HT output to the joint point of L502, C513, C512. Also make sure you get power on the final transistors. You can check this without feeding any RF signal.

AC0FP
09-04-2009, 08:07 PM
Those are PNP transistors, so they're a little harder to work with in 12v negative ground applications.

IIRC, the 22 is about .4 watts in, and 4 out, the 23 is about 15-20 watts out, the 24 is about 35 and the 25 is about 60 watts out. They are not real high gain transistors, these are from the early 70's.

The 23 or 24 would probably make a pretty good amp for 5 watts in. The problem will be the design, and whether it's worth it.

Joe

I thought those numbers sounded familiar, PNP's ugh! I took all of the PNP Micor PA's and chucked them. I kept the modulator and exciter and replaced the finals with a Motorola NPN 40 ~ 50 watt power module. They worked fine in repeater service because the radio had a nice heatsink!

73,

:)

K7JEM
09-04-2009, 08:14 PM
I thought those numbers sounded familiar, PNP's ugh! I took all of the PNP Micor PA's and chucked them. I kept the modulator and exciter and replaced the finals with a Motorola NPN 40 ~ 50 watt power module. They worked fine in repeater service because the radio had a nice heatsink!

73,

:)

Yes, the PA is really the only weak point of a VHF Micor. The receivers are excellent, as are the exciters. Most people have no problems with the PA's, but they can be a bear to troubleshoot.

One big problem with using a Micor on 2M is that most of them are the 150-162 version. These require some mods to get the PA to work right. Sometimes they will work OK down to 147 or so, but when you get much below that, you start to have issues.

Joe

KM3F
09-04-2009, 08:59 PM
Respectfully, besides the learning and finance part, you will end up either spending more on this project or abandoning it than buying a unit from the clasiffieds. Many are showing up at less than $200 and often in the $150 or less range and you can get as high as 160 watts with full drive.
Remember you still need at least a 10 to 20 amp power supply to run an amp of any reasonable and worthwhile power level that adds to the total cost.
If you still feel cost is a big factor I would consider a single rf power transistor of the T220 or simular package as a single that you can get as high as 50 watts from and not have half the hassle as well as straight forward building.
The circuits as 'test' circuits are many and just need packging for your application.
For example, my Yeasu 2800 mobile uses a single RF device instead of a module and runs 50 watts on high. The radio is now just out of production and may still be found at dealers and about $200 on the used market. They take about 10 amps on high power setting and have all the features plus weather and scanning below and above 2 meters.
In any event good luck.

KC9OXP
09-04-2009, 09:07 PM
Starting to wonder what the mod is to brig the PA part down, I pump in 5 watts and don't really get any thing, but when i trigger an oscillation, it goes! I checked the oscillations with a spectrum analyzer and its to much splatter to tell what its at.

AD2U
09-04-2009, 09:10 PM
Starting to wonder what the mod is to brig the PA part down, I pump in 5 watts and don't really get any thing, but when i trigger an oscillation, it goes! I checked the oscillations with a spectrum analyzer and its to much splatter to tell what its at.


Do you have a scope? That will make the process easier as the waveforms are shown on the service manual.

Without a scope, you can get by with a VOM meter, but that is much much more difficult and uncertain.

K7JEM
09-04-2009, 09:12 PM
Starting to wonder what the mod is to brig the PA part down, I pump in 5 watts and don't really get any thing, but when i trigger an oscillation, it goes! I checked the oscillations with a spectrum analyzer and its to much splatter to tell what its at.

That was the big problem with these amps. They would tend to self oscillate under some conditions.

Unless you just have to use this amp, I wouldn't. There are so many better things available, at little cost.

I have been a radio tech for 30+ years, and I would not attempt to build an amp from this board. While it could be done, it is not easy and subject to a lot of problems. Not a good project for a person not familiar with RF power amp construction.

What are you wanting to do? What is the goal you want to accomplish?

Joe

AD2U
09-04-2009, 09:22 PM
Unless you just have to use this amp, I wouldn't. There are so many better things available, at little cost.

How about Motorola GM300 PAs?

K7JEM
09-04-2009, 09:25 PM
How about Motorola GM300 PAs?


Those would probably work good. About 20 years newer, too.

KC9OXP
09-04-2009, 09:28 PM
Ya I have an oscilloscope, that is what I am using to measure gain if any. Its not digital but it is a late 80's early 90's military scope i got at a military surplus store. Unfortunately i think my scope's band with stops a little past 100 MHz. When I look at the oscillation, they are just look a thick bandwidth signal with occasional strong patterns.

As for:
What are you wanting to do? What is the goal you want to accomplish?

I am wanting to turn it into a functional 2 meter amp.

The goal is to not only have a functional equipment, but to help me learn and understand. I have a lot of books, but I am a hands on learner.

KC9OXP
09-04-2009, 09:42 PM
Well, I am going to put it aside for the rest of the day, get some other work done.

WA7KKP
09-05-2009, 06:44 PM
I am trying to build a 2 meter amp with a salvaged radio. It is an old train radio so I know They will bump down to 2 meters. Now what I don't know if is it ran on FM or AM.

If it is an AM radio will the transistors still work for FM of same frequencies?

Does any one by chance have a schematic or data sheet for-
M9622, M9623, M9624, M9625?
Don't waste your time Google those, their is nothing, but web sites in china that says they will sell them to me, but they seem to be fake sites, you can type a fake number and it will pop up they have it in stock.

I am currently trying to reverse engineer the board, the way it is set up now I can not trigger them. I think the circuit is just to well tuned. I can how ever remove a capacitor and strike it with RF and get a very strong oscillation so i know they are still good.

The transistors I am trying to use have four leads. They are probably from the late 60's to upper 70's judging by the way the radio looks.

Railroad radios are FM, in and around 160 MHz.

The numbers you quoted are Motorola part numbers. I'm not that MOTO savvy, but these sound like the transistors from a Mocom-70 PA deck. These took about 1/2 watt drive from the exciter board and boosted them to about 50 or 100 watts depending on version.

Easiest way to use this ---- is to put a resistive pad on the input to absorb the excess power from your driver (1 or 10 watts?), and add some sort of RF sensed T-R relay. You can have 12v applied all the time they are class C zero bias, so there won't be any current draw until RF is applied. The saying here is -- don't reinvent the wheel if you don't have to . . .

The four leads of the transistor are collector, base, and TWO emitter leads, 180 degrees opposite. They are wide and flat for good low-inductance leads to the actual transistor chip inside. Solid state amplifiers are known for very low input and output impedances, on the order of a few ohms at best.

Gary WA7KKP

KC9OXP
09-06-2009, 08:11 PM
OK. After studding the schematics and troubleshooting.
Q M9622 Fail (Pre)
Q M9623 Fail (Driver)
Q M9624 Pass (Final)
Q M9624 Pass (Final)

So now I am wondering if I can drive the finals on 5 watts even if their not at their full peak. If not is it possible to bias them just ever so lightly so the 5 watts will trigger them?

KC9OXP
09-07-2009, 01:29 AM
I have kinda abandon that radio, I have now a MOTRACK its been robbed of xtals. I have all ready tapped into it and I can use the tubed finals. I am going to part up the other radio and use the band pass and other RF components in it to make this new radio amp.