UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Audio (record players, hi-fi etc)

Notices

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

Reply
 
Thread Tools
Old 5th Aug 2018, 11:57 pm   #1
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default 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?
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 6th Aug 2018, 12:16 am   #2
Techman
Octode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 1,888
Default 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.
Techman is offline   Reply With Quote
Old 6th Aug 2018, 12:21 am   #3
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default 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?
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 6th Aug 2018, 12:29 am   #4
Techman
Octode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 1,888
Default Re: Dansette Major Deluxe - too quiet

Quote:
but what else is there in this rudimentary amp to try?
Not a lot. Guessing you did the test with the volume control at full?

Using the EL84 data and measuring the crucial pin voltages should soon have the problem pinned down.
Techman is offline   Reply With Quote
Old 6th Aug 2018, 12:35 am   #5
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default 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.
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 6th Aug 2018, 12:39 am   #6
Techman
Octode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 1,888
Default Re: Dansette Major Deluxe - too quiet

I'm guessing there'll be a resistor down - or perhaps I should say high.
Techman is offline   Reply With Quote
Old 6th Aug 2018, 1:46 am   #7
Techman
Octode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 1,888
Default 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.
Techman is offline   Reply With Quote
Old 6th Aug 2018, 6:14 am   #8
Edward Huggins
Dekatron
 
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 4,555
Default 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.
__________________
Edward.
Edward Huggins is online now   Reply With Quote
Old 6th Aug 2018, 6:26 am   #9
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 3,742
Default Re: Dansette Major Deluxe - too quiet

Also check the pots resistance - wiper to ground at full volume.

Good luck, Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Old 6th Aug 2018, 8:27 am   #10
slidertogrid
Heptode
 
Join Date: Apr 2005
Location: Peterborough, Cambridgeshire, UK.
Posts: 811
Default 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
slidertogrid is offline   Reply With Quote
Old 6th Aug 2018, 8:46 am   #11
Michael Maurice
Moderator
 
Michael Maurice's Avatar
 
Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 5,351
Default 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.
__________________
Forum Moderator

www.michaelmauricerepairs.co.uk
Michael Maurice is offline   Reply With Quote
Old 6th Aug 2018, 2:37 pm   #12
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,251
Default 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.
Studio263 is offline   Reply With Quote
Old 7th Aug 2018, 2:08 pm   #13
Techman
Octode
 
Techman's Avatar
 
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 1,888
Default Re: Dansette Major Deluxe - too quiet

Quote:
Originally Posted by Studio263 View Post
Shorted turns in the output transformer would be my guess
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.
Techman is offline   Reply With Quote
Old 7th Aug 2018, 2:34 pm   #14
Edward Huggins
Dekatron
 
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 4,555
Default 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.
__________________
Edward.
Edward Huggins is online now   Reply With Quote
Old 7th Aug 2018, 5:13 pm   #15
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default Re: Dansette Major Deluxe - too quiet

Story so far - rectifier checks out OK.
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 7th Aug 2018, 6:07 pm   #16
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default 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?
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 7th Aug 2018, 11:00 pm   #17
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 4,936
Default 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?
__________________
'And, in the end, the love you take is equal to the love you make'
The Beatles.
Sideband is offline   Reply With Quote
Old 7th Aug 2018, 11:16 pm   #18
RojDW48
Octode
 
RojDW48's Avatar
 
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 1,417
Default 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?
__________________
'....don't go mistaking Paradise for that home across the road!' (Bob Dylan)
RojDW48 is offline   Reply With Quote
Old 8th Aug 2018, 12:16 am   #19
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 6,844
Default 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 .....
__________________
Julie {formerly known AJS_Derby}
julie_m is offline   Reply With Quote
Old 8th Aug 2018, 5:47 am   #20
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 3,742
Default 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.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 4:28 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.