Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.

[Station X]

Circuit should look something like this, although the need for the choke is doubtful.

What's the value of the smoothing capacitor?

[ms660]

If it's LC then the B+ supply to the amplifier under load would be lower than it would be if it were C or CLC.

Lawrence.

[vidjoman]

I think this is the original Radiospares circuit diagram, or part of it.

[Refugee]

Originally Posted by Station X

Which transformer is that? I think you may be referring to the unnecessary output transformer which was discussed up thread.

Yes that is the one.
With those hand written numbers I would say custom wound for an unknown original use.
That valve power supply choke will have far too much resistance to be in series with the power for a small transistor amp. They normally just have a single capacitor.
It looks like an abandoned project and may never have worked from the start.

[DMcMahon]

Originally Posted by Refugee

There is also a transformer of unknown heritage between the pickup and amplifier most likely added because the pickup was duff.

From previous it looks like the output transformer is connected between the amplifier board and the speaker.

David

[Refugee]

We still do not know if it was even meant to be an output transformer.

[DMcMahon]

Yes very true.

David

[peter_sol]

I think that transformer connected to the speaker is an RS. ( Radiospares) matching transformer. The IC needs 8 or more ohms and no doubt the speaker is a 3ohm one.
The clue is, the snap on cover.

[Bigears]

That's a big possibility and I may think you are right

[Edward Huggins]

Originally Posted by peter_sol

I think that transformer connected to the speaker is an RS. ( Radiospares) matching transformer. The IC needs 8 or more ohms and no doubt the speaker is a 3ohm one.
The clue is, the snap on cover.

The 7" x 4" Elac speaker, now seen in the photo, is 99% likely to be 3 ohms.

[Bigears]

today I found a broken wire on the output transformer I did a repair now I hums and crackle from the speaker, please see picture regards Ken

[Station X]

Does it now pass the "buzz test"?

Even if it does you'll still need to sort out the power supply for best performance.

[DMcMahon]

Originally Posted by Bigears

today I found a broken wire on the output transformer I did a repair now I hums and crackle from the speaker, please see picture regards Ken

Well that is some progress back to how it was. Is there any identification marks on the output/matching transformer ? would be good to know if it is correctly connected.

Still would be good to get a drawing of the actual power supply wiring connections. Does not have to be a technical drawing just a simple hand drawn sketch showing the mains transformer, bridge rectifier, choke and smoothing capacitor (just drawn as rectangles) showing the wires connections and any terminal identifications on the parts. This is important because there are still unclear questions as to how the mains transformer secondary windings are connected, if the choke is actually required etc.

David

[Bigears]

Hi Please see drawing and picture regards Ken

[ms660]

It's as I thought on both counts (Post#47) series secondary's and LC filter so far as I can see.

Lawrence.

[Station X]

Looks like my drawing in post #101.

I don't understand the spec of the choke though.

Should be something like x Henries at y mA.

[DMcMahon]

Well done Ken that clarifies the power supply wiring a lot. The photo confirms that the mains transformer primary is correctly connected.

Can you measure the voltage arriving at the choke input and re-measure the voltage at the choke output to see how much voltage is being dropped across the choke and re-measure the voltage arriving at the amplifier PCB (previously there appeared to be a large voltage drop arriving at the PCB). The previous voltage at the smoothing capacitor seemed somewhat on the low side for the series connected secondary expected output.

Important to do the buzz test from Post # 56 (it is safe to do), this will help to prove if there is any life in the amplifier.

David

[Bigears]

Sorry Dave I did the buzz test just before I sent the last pictures and it worked fine but forgot to include it with the pictures

[DMcMahon]

Originally Posted by DMcMahon

Would be good if you could identify/close up photo the actual cartridge/stylus that is fitted, especially if it turns out to be a bad cartridge.

David

This is still a valid question especially as the hum test looks like there may be some life in the amplifier.

David

[Bigears]

I am getting a reading from the smoothing choke capacitor of 8.28v
A reading from the smoothing choke 2.45v

the input to the mother board is 8v