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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 27th Nov 2020, 9:24 pm   #21
cdm1christopher
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Default Re: Identification of unknown PA amplifier

Em lost me there not enough semi conductors? How many should there be on the module? What's not matched? If you let me know I'll check them. All numbers on the components match up?
Checked voltages etc and all seems fine within component specification sheets. All I've done is changed out the dual capacitors all blown each can was x 2 2200uf 63v each making a total of 4 cans. I've put 4 single 6800uf 100v caps in there and two new 22uf caps in again 63v but upped to 80v.
Anyhow if you can point out what's missing would be helpful otherwise it's not going to work I would have thought. It will get a run on a CD tomorrow so I'm sure that will tell if parts are missing.
I'll take some better pictures of the boards and the bridge rectifiers which are on the same bar as the tranny.
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Old 27th Nov 2020, 9:28 pm   #22
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Default Re: Identification of unknown PA amplifier

Ah yes I see the different codes there but they come as a pair I looked that all up. They're not meant to be matched.
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Old 27th Nov 2020, 9:33 pm   #23
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No there's nothing missing Chris, it's just as Trev said, you would expect there to be more transisitors before the drivers but I suppose it is a very basic no frills circuit.
I have a Lyon Forge amp here that just seems too simple to work but it does.

Edit: The outputs are a complimentary pair. I just saw the 2S and the 4 on the end and assumed (wrongly) that they were both the same as is quite common.
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Old 27th Nov 2020, 9:43 pm   #24
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Default Re: Identification of unknown PA amplifier

Oh okay I had to scratch my head then as I had it apart checked codes on the parts not easy to find all obsolete well originals and could not see anything missing either. I think it runs along the lines of a push pull class A/B type. Could be wrong.
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Old 27th Nov 2020, 9:51 pm   #25
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You would expect a couple more transistors between the input IC and the drivers but obviously not in this case.

I often search for older parts on ebay and try to get good working used or new old stock. There's always someone clearing out parts for one reason or another.

David.
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Old 27th Nov 2020, 10:17 pm   #26
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Default Re: Identification of unknown PA amplifier

All interesting stuff. One thing I have learned is more is not necessarily better. Looks good though.
Yeah I'll keep an eye out for parts if needed.
Cheers Chris
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Old 27th Nov 2020, 10:19 pm   #27
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Ooops not sure why I put that pic in there.
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Old 27th Nov 2020, 10:29 pm   #28
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Yeah Wrong section. Unless of course, you were going to ask about converting it into a guitar amp

David.
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Old 27th Nov 2020, 10:33 pm   #29
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Evening Chris and Dave
Chris can you give me the marking of the Op amp integrated circuit on the board ?
If it works I'm all for a minimum part count
Chris are you able to trace the circuit ?
looking at the components etc on the board I feel its a Texan derivative But I am actually excited re the schematic
Can you tell what the voltage of the power rails are
This will give us a good idea re power output etc.
Trev
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Old 27th Nov 2020, 10:33 pm   #30
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Ha ha ha �� that's funny a superhet into a guitar amp be interesting.
I thought it was a pic of the shot caps in this unit. Pushed wrong pic.
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Old 27th Nov 2020, 11:05 pm   #31
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Default Re: Identification of unknown PA amplifier

I'll re measure tomorrow hopefully not shorted anything.
The board is marked CPA10:4 TB. Not been able to find anything about it. Looking at it pic attached I've just noticed the 3 solder points and two screw holes. I wonder if there was another unit in there? Or modification done and that part no longer required? Did not notice that before! Rule of thumb look more than once.
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Old 27th Nov 2020, 11:12 pm   #32
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Default Re: Identification of unknown PA amplifier

Quote:
Originally Posted by cdm1christopher View Post
Looking at it pic attached I've just noticed the 3 solder points and two screw holes. I wonder if there was another unit in there? Or modification done and that part no longer required? Did not notice that before! Rule of thumb look more than once.
They probably used the same PCB for more than one type of module. There was probably a module that used a higher power supply voltage with an extra pair of output transistors to give more power.
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Old 27th Nov 2020, 11:27 pm   #33
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Yes James, that's exactly what they did.
If you look at the picture Chris took of the board in the first posts, you will see a space for 2 more devices on the heat sink.

David.
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Old 27th Nov 2020, 11:43 pm   #34
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Default Re: Identification of unknown PA amplifier

What are the part numbers on the black transistors on the small heat sinks?
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Old 28th Nov 2020, 7:42 am   #35
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Pair of 8223 tip30c and pair of 8223 tip34c. It looks like they are knocking the voltages out of phase 180 waveforms. Again still cannot find the part code 8223 tip30 fine loads of different ones. These also have made in Italy stamped on the metal heat sink.
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Old 28th Nov 2020, 7:57 am   #36
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Default Re: Identification of unknown PA amplifier

I think that's right codes I'll look again later as there bit rubbed.
Another interesting thing which I've never come across is the larger resistors all the leads are looped then soldered in. So that was to remove heat from the board. So this must get pretty darn hot when running. Also the bars connecting the speaker outputs together is about 3mm in diameter thats big.
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Old 28th Nov 2020, 8:56 am   #37
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Default Re: Identification of unknown PA amplifier

Phew that that transistor okay 1.3v all okay just blew the 2 fuses good protection circuit in there.
Lucky got ten as there are 4 F5 fuses in all. 2 for each board. Plus mains fuse t6.3v.
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Old 28th Nov 2020, 11:01 am   #38
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Default Re: Identification of unknown PA amplifier

TIP30(C), TIP34(C) are common Texas parts. 8223 is date code, week 23 1983. The C suffix relates to voltage rating of 100V.
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Old 28th Nov 2020, 1:38 pm   #39
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Default Re: Identification of unknown PA amplifier

Ah nice one so it's a texas model then? Funny because it was last PAT tested in 1983 when that part was made. well I've definite blown it for sure. All hooked up left channel perfecto the right dead as a door nail on switch on thump fuses went. So now on hunt for replacement part I'll have to check whole board make sure nothing else has gone. Odd part as only two legs are connected the third leg looks like its been cut. Or is it linked to ground via the heatsink plate on the back.
Soundwise with no tone controls pretty good through the PA speakers. Surprised there. Output I reckon tops 60/80 watts. The PA speakers through my mono block quad blow the house down its unbearable everything including me was vibrating. Lasted 5 minutes then turned straight down. Had this turned up halfway no where near as loud. But then you can't really compare it to valve gear not a fair comparison.
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Old 28th Nov 2020, 2:34 pm   #40
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Default Re: Identification of unknown PA amplifier

This has inspired me ! Well in a way it has I have taken a texan from the to do shelf simple fault blown output pair
The texan was always marginal in this respect !!
Having said that I would love to see the schematic from yours as with the parts as shown
It cannot be much different
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