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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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5th Aug 2018, 11:57 pm | #1 |
Nonode
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Dansette Major Deluxe - too quiet
This is faintly embarrassing - after all there is hardly anything in this little amp! But the volume is very low. The TC8? has been replaced with an X5H (that should be alright, shouldn't it?). I replaced the 0.05 uF cap and swapped the EL84 - all to no avail. The sound is OK - just very low - any ideas?
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6th Aug 2018, 12:16 am | #2 |
Dekatron
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Re: Dansette Major Deluxe - too quiet
The X5H may well be faulty - buzz test will confirm, but careful with possible live chassis and dodgy isolation to pickup.
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6th Aug 2018, 12:21 am | #3 |
Nonode
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Re: Dansette Major Deluxe - too quiet
I did the buzz test - that was rather too quiet as well - made me suspicious....but what else is there in this rudimentary amp to try?
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6th Aug 2018, 12:29 am | #4 | |
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Re: Dansette Major Deluxe - too quiet
Quote:
Using the EL84 data and measuring the crucial pin voltages should soon have the problem pinned down. |
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6th Aug 2018, 12:35 am | #5 |
Nonode
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Re: Dansette Major Deluxe - too quiet
I did - and I have the pin voltages to hand - I shall wield the multimeter and report back - thanks.
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6th Aug 2018, 12:39 am | #6 |
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Re: Dansette Major Deluxe - too quiet
I'm guessing there'll be a resistor down - or perhaps I should say high.
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6th Aug 2018, 1:46 am | #7 |
Dekatron
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Re: Dansette Major Deluxe - too quiet
Actually, seeing as it's a simple single stage amplifier needing a high output from a cartridge to drive it, you won't get much of a buzz from it, so could still be a bad cartridge.
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6th Aug 2018, 6:14 am | #8 |
Dekatron
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Re: Dansette Major Deluxe - too quiet
Suspect a low HT from the contact cooled rectifier. If you are lucky enough to have another high output cartidge to hand, try this as well.
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6th Aug 2018, 6:26 am | #9 |
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Re: Dansette Major Deluxe - too quiet
Also check the pots resistance - wiper to ground at full volume.
Good luck, Andy.
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6th Aug 2018, 8:27 am | #10 |
Octode
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Re: Dansette Major Deluxe - too quiet
Check the HT is correct, the contact cooled rectifiers sometimes fail. I had a Bush with only 90v HT due to the rectifier it still worked with no distortion but the volume was fairly low.
Check the HT on the smoothing capacitor if it's OK there check the voltage on the anode pin of the valve is the valve getting hot as normal? As you say there isn't much to it.. can't be too Major... Rich |
6th Aug 2018, 8:46 am | #11 |
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Re: Dansette Major Deluxe - too quiet
I've never experienced a problem with these rectifiers, check screen grid resistor and cathode bypass resistor and capacitor, I actually replace all capacitors in these as they are very prone to failure. I’ve also had the odd EL84 cause low volume for first 20 mins or so.
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6th Aug 2018, 2:37 pm | #12 |
Octode
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Re: Dansette Major Deluxe - too quiet
Shorted turns in the output transformer would be my guess, assuming that the cartridge is OK (still the most likely suspect). If the cathode voltage is about right the emission of the valve must be reasonable, so what else is left?
You'd need to check the inductance to prove this, voltage and resistance checks won't show anything amiss. Trying a transformer from another one (or any other radio, TV, tape recorder etc with a similar output valve) is the quickest way to rule it in or out. |
7th Aug 2018, 2:08 pm | #13 |
Dekatron
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Re: Dansette Major Deluxe - too quiet
That's a bit drastic!
I had considered that possibility, but thought it to be fairly unlikely in a record player like that, although there's always a first time for everything, and just because I haven't encountered it before, etc. If it's not low HT or a missing/low voltage on anode or screen, I reckon it'll turn out to be the cartridge, as the buzz test on these simple amplifiers needs a bit of experience to determine the level expected, which is going to be quite low even on full volume. |
7th Aug 2018, 2:34 pm | #14 |
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Re: Dansette Major Deluxe - too quiet
If it is the OPTX (I also doubt this) do not replace it with another "Midget" type as currently fitted. The earlier Dansette single-stage amps (UL41/UL84 c.1954/55) used a more generous tranny and this resulted in a far fuller sound. Mind you, the Fidelity models used one even smaller.
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Edward. |
7th Aug 2018, 5:13 pm | #15 |
Nonode
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Re: Dansette Major Deluxe - too quiet
Story so far - rectifier checks out OK.
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7th Aug 2018, 6:07 pm | #16 |
Nonode
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Re: Dansette Major Deluxe - too quiet
EL84 voltages pin 2 = 0V, pin 3 = 6V, pin4 = 6.3VAC, pin 7 = 225V, pin 9 = 225V. Looking at previous posts about this RP that doesn't look too out of the way? Maybe the voltage at pin 3 a bit low?
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7th Aug 2018, 11:00 pm | #17 |
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Re: Dansette Major Deluxe - too quiet
Pin 3 (cathode) could be a bit low....my experience with these is that the cathode should be between 9 and 12V. Not a lot to cause this. The screen grid seems about right but I thought the anode should be higher. I wonder if it is coming back to the output transformer? Have you got something you can try in there?
I presume the screen grid is fed from the smoothed HT and the anode is fed from the reservoir. The HT smoothing resistor is around 10-15K?
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7th Aug 2018, 11:16 pm | #18 |
Nonode
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Re: Dansette Major Deluxe - too quiet
I think I have a working TC8M in my bakelite rim drive deck - I should be able to patch that in to test cartridge before I start replacing more components. I guess there is not a lot of point patching a CD player (my usual fallback) as it wouldn't have a big enough output?
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8th Aug 2018, 12:16 am | #19 |
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Re: Dansette Major Deluxe - too quiet
If you've got another device with a single EL84 amplifier, you could feed your CD player into that and see what sort of volume is reasonable to expect .....
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8th Aug 2018, 5:47 am | #20 |
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Re: Dansette Major Deluxe - too quiet
A CD player should have more OP than a cart. Have you got a sig gen or phone app/audacity you can stick a signal in with? If we had some numbers we could say if the amp is at at fault, EG 0.5v in 3v out.
Andy.
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