Super jopix 1000 no tx problem

[Handy Andy]

Good Morning!

IT has to do with how the AM Regulator can also be a power switch for SSB modes.

Good morning, another doubt I have. Later I will check previous answer when at home. How 12.5 volts in tr51 base is achieved? It is. Another voltage is under the specification, but I can't see in schema how 12.5 volts can be generated...

How that works is by using two Transistors - TR52 and TR54

One works for FM and SSB modes - it turns (mutes) off audio by shuniting it to ground (TR54)

TR52 - keeps AM out of your FM mode - but ALLOWS for Carrier to be adjusted as if it was AM - this keeps the Final and Driver from overheating - FM mode is pretty hard on devices and consumes to the most power in the radio for that mode. Bandwidth is needed so you set up AM and FM modes with AMP VR13 for carrier - when in FM mode or SSB, the AMC amp TR53 is pretty much disabled.

TR52 works as a means to BYPASS any envelope developed in TR 51 and TR50.

So the battery voltage supply - is from the MODE switch routings to the various switches that turn on or off the AM Regulator sections for Audio or Envelope - SSB (TR52 and TR54) mode allows for full rail voltage, but in FM mode you don't want that on this design. (TR54 only)

 

[NODENS]

Today, lost on modulator area, no advance . I can't discover why volts are a lot below specification in that area: tr49, tr50, tr51.

Tr 51 only have the volts right in emitter, base and collector 2.6 volts only. Tr50. and tr 51 are below by far the specs also. Tr 52 same in collector where should be 5.6 volts and only around 2.5 present. Where are the volts hehe???? Seems hard to find all those missing volts (I'm testing an am, but all bands equal (and removing tp7_8_9). I will see if equipment transmit when at least required volts in modulation area is normal but.... Any ideas to try???

By the way I tested the capacitor described upper in previous posts and was OK... Too

 

[Handy Andy]

When voltage is low, Suspect the VR13 - it is supposed to supply about 4 to 5 volts. Then the only other SOURCE for power is thru R240.

C189 is a hi-pass filter (so you have a treble roll off result in regulation) and floats envelope power thru R241 and C190

That gives you 4 ~ 5 watts - adjusted thru VR13. But you need R141 to be 560 ohms - no more no less to bring voltage up so suspect R240 as having the wrong value. C189? Should be ok but check - you can use this part to change the tone in the Audio - need more Treble? LOWER value to say 0.01uF (103) want more Bass? (within reason) bring C189 to 0.47uF (474)

C190 adjusts envelope effects and provide more bandwidth for tonal effects applied on C189 - C190 at 100uF is about as much as you can go - lowering this value brings up a level of compression with less envelope to play with for bandwidth Raising the value improves bandwidth and bass response - too much she will squeal on you.

 

[NODENS]

Vr13 seems OK voltage supplied is Dow to 3volts more. Or less thought 2 resistors to tr49 base. I think the missing voltage part from the other path can be due to as tr 51 not have 12.5 volts in its base, not enough current is arriving to the second path for tr49 base from tr51 collector. Why tr51 base can miss almost 10v in its base? Can be this the issue?

 

[Handy Andy]

Has TR51 been replaced?

It is a PNP (2SA1012)

But Tr50 Is it ok?

And do you have a 10K at R242?

As a test, remove TR52 and recheck TR51 to see if voltage recovers.

If so Replace TR52 with 2SC945 - else re-install ORIGINAL part.

Let me know your results...

 

[NODENS]

OK I will check that, tr 51 was replaced yes as a test by new one (same model) Tr 50 I removed, test and as the measurements seems OK I place again. I will check other points I will you know the results.

Thx mate, I'm learning. A lot with this equipment

 

[NODENS]

Hi mate I was testing a bit today with your. Comments.
Tr 50 extracted and seems it is fine with multimeter.
R242 10k OK, checked with multimeter too.

TR52 Removed, no changes in tr 51 voltages in base and collector (2.x volts).
I checked vr13 path again and seems fine with voltages.

Tomorrow I will extract tr51 and will recheck it (I supposed was fine as was changed with a new one....


Any other possibility I'm not seeing could impact getting down. Volts in tr49, 50 and 51 comparing with specs for am? (the band I test but all are the same)

 

[Handy Andy]

Actually, check SSB - RX mode, you should get 12V or thereabouts when you look at TP 9 to FOIL (not case)ground.

Then it means SSB switch ok.

When you have voltages that are so low, then I'd look at leaving the radio on - Test point Jumper board removed and leave it on for 15 to 20 minutes and start feeling the traces back there at the AM Regulator for heat - because if something is pulling down the lines - that should show up as a hot spot and localize the low-voltage problem.

C193 is a cap that can goof things up but ... if the above test passes - then that cap is not bad. Age of the radio though - I'd replace it for cheap insurance. IF the cap got leaky, it can pull power from the line it uses - but if TR52 got pulled and no change - then C193 can be left alone...

Don't keep changing parts unless you're sure - test first - so leave new part in for now - for if old part and new part perform the same then that was not the reason for the low voltages.

I'd also look at seeing what is going on back further in the power feed to that section - are there any blown caps or is the power choke funky...

As well as after TR51 - in fact pull the test jumper and see if TP 9 recovers - there may be parts further down the line that are sucking all that current.

Is D91 still show as a good diode - one way valve? Can upset the applecart if shorted...

Attaching a simpler design, to show you voltages you should be getting for that radio...remember to check these voltages to known Ground - not Case - your power supply negative.

 

[NODENS]

Mate Thx for your support, Finally I put. Out. Tr51 legs to. Measure.... Base-emitter is open... Seems that was my second fault with R237 detected previously, I don't have replacement now I will search and I will change in few days.... Seems like some new components can come not very good state.... But Thx a lot really, you teached me a lot. I. Will finish this post when I can verify after replacing that is. OK all now

 

[NODENS]

Good afternoon, I replaced tr51 yesterday, I could not go to buy new one before. That radio is going to be Funny. Now I can obtain swing up on radio meter when transmitting and I have the carrier output, but voice is not being modulated, only carrier at output.

I will try with oscilloscope to track micro signal from beginning trying to See where it is lost (is that possible??)

Any additional ideas are wellcome. At least, I'm learning a lot.

 

[Handy Andy]

Check Mode - AM and FM. There is a ground switching transistor that "mutes" audio. Another that controls Carrier power - AND audio for SSB mode. A THIRD one handles AMC...

For DIAGNOSTICS purposes, the best way to restore or check audio - is by removing TR54, TR53 and TR52 - then use ONLY AM mode - and see if audio returns.

If it doesn't - stop here and inform us...you may have a failure in the audio chain even limiter section can kill audio.

IF it does, (Audio Returns) replace-reinstall TR54 - Still have audio? Then that switch handles AM and FM toggle - so we should leave that alone.

Only other two are the AMC limiter amp - TR53 and SSB/FM Power Switch - TR54.

Replace these one at a time and re-check operation as you complete the stage...

The one that makes the audio "mute" or quit - is your suspected part or parts within that stage are suspect.

TR 53 is a tricky one, for it is the limiter and trim for AM.

 

[NODENS]

No luck Andy I removed 3 transistors and same situation, meter swing up when transmitting but no audio. And no meter vibration while talk.

I tried to put an small oscilloscope to test audio on mic gai pot (ground on chasis) and I can see only a wave that is not oscillating if I talk to micro (not sure if this is a good testing). I thought I should see the audio as micro audio pin is connected to mic gain pot, but no luck. Which is the audio path from micro? Can I test it?.

Thx mate

 

[NODENS]

I could not trace the audio for the moment. I will try if I not find any other solution to inject 1khz tone starting from mic gain pot and following the path (I believe I have clear that now) in am trying to see in which moment I hear the transmisión in another portable radio I have. I hope not destroying the radio with this test

 

[Handy Andy]

Use dummy load and keep power wattage down - like 2 watts or less - keep finger on back panel - if yo take too much time to do this test you can heat that finals section up - so be patient and work in steps and stages - this isn't a marathon. Or maybe it is - just don't be the rabbit and lose the race trying to hurry thru it...

 

[NODENS]

This equipment was fixed, I forgot to answer and thanks Andy and rest of people trying to help. Finally, modulation loss was due to modulation pot that was defective, once changed, modulation backs again. Thx all friends