Dansette Major capacitor

[lesparapluies]

Just had another interesting session tonight. I replaced the selenium rectifier with a 1N4007 in series with a 150Ω resistor, not much change. I then connected the earphone output of a transistor radio to the input of the amp and got quite a nice sound from it. Voltage measurements were: HT line 206V, cathode of EL84 about 4.5V, grid about -200mV. I then connected it to the "new" BSR cartridge (second one I've been sent) and nasty distortion (not "overload" distortion but just a dirty sound at a medium volume) - I tried various stylus weight settings but no difference. Unless anyone can suggest anything I've overlooked, I'm coming to the conclusion that both the new cartridges I've been sent are faulty, maybe a bad batch?

[Edward Huggins]

If you are getting decent sound from a radio input, there's not much else in this very simple amplifier that will need checking. We can assume the cathode bias resistor, the output transformer and speaker are all good. The H TC8 I bought from your supplier worked just fine, but there might be a batch problem with yours.

[lesparapluies]

Thanks everyone for recent replies. I'm a bit stuck at the moment, having returned the possibly faulty cartridges to the supplier and waiting his verdict. Today I went for a bike ride and thought about ways round the problem. I've got a perfectly good deck, good amp and reasonable cabinet. I'd like to get it working in some shape or form without too much outlay, ideally using what I've already got in stock, and I thought of a couple of solutions; these may or may not be feasible, so any thoughts appreciated. Both involve boosting the gain of the amp so I can used a ceramic cartridge, more obtainable and cheaper, and I think I've got one or two lurking somewhere. OK, solution one would be to modify the circuit to use a single ECL82 as a 2-stage amp which I think would then have sufficient gain; I remember repairing a radiogram which used an ECL82 and a ceramic cartridge - but I have a feeling the existing output transformer (EL84) may not match? Possible solution no. 2 is a bit more far-fetched - to make a little transistor pre-amp circuit for the front end, perhaps a 2N3904, could power be taken from the 6.3V heater winding, bridge rectifier and smoothed to give about 9V.. or am I "getting into the realms of fantasy, Jones" as Captain Mainwaring might say? I can hear people saying "why bother?" and it's a valid point, but time is not an issue and it keeps me busy while my wife watches Strictly.

[lesparapluies]

Hello everyone and Happy New Year - just to report that Dansette have sent me a third cartridge, and this one is perfect, no distortion and a nice high output, so it looks as if the first 2 were from a faulty batch; thanks to all who contributed suggestions to this posting.

[Techman]

That just goes to show - I wasn't expecting that!

They obviously don't test them, so something for anybody buying one to be aware of. I wonder whether they're old stock that they've found somewhere or whether someone is refurbishing old ones and isn't fully testing them before supplying them to the company. It could also be ones that have already been sent back as faulty and not tested before being sent out again, probably just assuming that the purchaser had got it wrong and the fault was with the amplifier...it would be interesting to know, although being non-compatible mono cartridges, I can't see a great demand for anyone wanting to fit one other than for absolute originality.

[Edward Huggins]

These H TC8 (and M TC8) cartridges are not the original BSR manufacture. They are far eastern newly made clones. That might be why thet are not designated TC8 H or TC8 M.

[tracypaper]

The old TC8H orange cart gave out 1volt, you are now saying the replacement is giving out 2 to 3 volt, that's why it's distorting.
Just remembered, I have just had a Japan made yellow X3H BSR copy which looked quite new, and that sounded terrible too, put an original BSR on and it sounded great.
Guess the clones/copies are rubbish made.
Gaz.

[lesparapluies]

Originally Posted by tracypaper

The old TC8H orange cart gave out 1volt, you are now saying the replacement is giving out 2 to 3 volt, that's why it's distorting.
Just remembered, I have just had a Japan made yellow X3H BSR copy which looked quite new, and that sounded terrible too, put an original BSR on and it sounded great.
Guess the clones/copies are rubbish made.
Gaz.

I hear what you say but the 2 faulty cartridges I was sent were not distorting because of too high an output - in fact the opposite, they were hardly driving the valve at all, which I appreciate makes little sense. But the distortion suggested something wrong inside the cartridge - in fact it was noticeable without even being plugged into the amp, the actual sound emitted "acoustically" straight from the record as it were, sounded dirty. I haven't actually checked the output voltage of the new good one, I may do that before I put everything back together just for interest.