Fidelity HF35T (Transistor version).

[HRichard]

No improvement with the correct cap installed.
All caps except the large smoothing cap have now been replaced.
All resistors checked.
All transistors replaced with checked working ones.
The only part of the circuit not touched is the component shown in image - I do not know what it is?
I am now led to believe the amp is working so issue must be elsewhere?

[Station X]

That's the bridge rectifier which converts the AC voltage on the mains transformer secondary winding to an unsmoothed DC voltage. This is then smoothed by the big electrolytic smoothing capacitor. What DC voltage do you see across the smoothing capacitor?

[HRichard]

Originally Posted by Station X

What DC voltage do you see across the smoothing capacitor?

26 volts

[Sideband]

Nothing wrong with the rectifier in that case!

It should be a fairly simple matter to feed an audio signal into the volume control of the amplifier from your phone or a similar source. If you have a transistor radio that you can access the volume control, you can easily extract a signal from there.

[Boulevardier]

Originally Posted by Sideband

Nothing wrong with the rectifier in that case!

It should be a fairly simple matter to feed an audio signal into the volume control of the amplifier from your phone or a similar source. If you have a transistor radio that you can access the volume control, you can easily extract a signal from there.

Agreed, we definitely need a known-to-be healthy input to test it. I do still wonder about that replacement cartridge.
Mike

[HRichard]

I'm still using the original cartridge. I haven't tried the new one since the first try didn't change anything. Thinking about it now though, I should try it again.
Also, in simple terms, how would I get a signal from my phone, for example?

[Boulevardier]

Originally Posted by HRichard

I'm still using the original cartridge. I haven't tried the new one since the first try didn't change anything. Thinking about it now though, I should try it again.

Very definitely. And tell us the result. You don't need to fully fit it at this stage. Just connect the slide on connectors to the new cartridge, and see if you get a response in the loudspeaker from gently stroking the stylus.
Mike

[Chris R]

In the absence of an audio source, you should be able to do the "buzz" test by touching the centre connection (wiper) of the volume control where it is soldered into the PCB. (Best done with the control at max. volume ) As mentioned in post #411, these pots are well known for heavy oxidisation of the internal parts and it could be the case that there is no continuity between the track and wiper.
They can often be restored by dismantling and cleaning, but getting them out of the unit takes a little dexterity.

Chris R

[Sideband]

Originally Posted by HRichard

Also, in simple terms, how would I get a signal from my phone, for example?

Well the headphone socket is likely to be the only output socket so that's where you get your signal from. Now you'll need a suitable lead with a jack plug of course and I'm betting that you won't have an old pair of earbuds lying about. What I have done in the past is bought a cheap pair of Poundland earbuds....they are very poor quality and sound like....well pretty rough! However if you cut the lead off, you will have an excellent way of connecting to your phone. Maybe instead of cutting the earbuds off, you can dismantle them and unsolder the connections which will give you a ready-made signal lead. Of course the lead will be stereo but it doesn't matter as you can connect either channel to the amplifier. Turn the volume on your phone to minimum to start with and the volume on the amp to maximum then slowly advance the volume on the phone. All being well you should clearly hear whatever is playing on your phone through the amplifier.

[Sideband]

I've lost track of a lot of this thread but have you actually tried a different speaker? It should be 8 ohms of course ( the same or higher than the one fitted but NOT LOWER). Just wondering if the speaker is completely seized and causing the low distorted volume.

[HRichard]

Monday update:

IT'S WORKING !!

Tried the new Chinese "red" cartridge and all is well, so it was the cartridge in the end although there was one faulty transistor and a mylar cap initially wrong with the amp.
Sorry it took so long but very grateful to you all for your help and patience.

At least now every cap and resistor has been replaced so should go for another 50 years

[Boulevardier]

Originally Posted by HRichard

Monday update:

IT'S WORKING !!

Well, thank god for that! I've been losing sleep over this one!

I think we had all been assuming that you'd left the new cartridge in the set since you originally fitted it.

Mike

[HRichard]

Originally Posted by Boulevardier

Well, thank god for that! I've been losing sleep over this one!

I think we had all been assuming that you'd left the new cartridge in the set since you originally fitted it.

Mike

I t made no difference at the time of first fitting so swapped back.
This was, of course, before C4 was found to be faulty