|
Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
|
Thread Tools |
22nd Jun 2022, 12:31 pm | #21 | |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,659
|
Re: Quad 303 pop on switch on
Quote:
https://www.vintage-radio.net/forum/...d.php?t=137769 The "vintage" RCA ones might be OK, but the new "Mexican" ones are likely to be the newer type of 2N3055 - which could prove "life-threatening" to the amp. Mike Last edited by Boulevardier; 22nd Jun 2022 at 12:51 pm. |
|
22nd Jun 2022, 7:05 pm | #22 |
Octode
Join Date: Aug 2008
Location: Rayleigh near Southend-On-Sea, Essex, UK.
Posts: 1,883
|
Re: Quad 303 pop on switch on
Hello,
Somewhere at the back of my mind I had 303 which ‘popped’ either when tuned on or off and it was caused by an open circuit diode MR100 or MR101. This was now 30+ years ago and I may be way off base here and I've got my knickers in a twist Terry |
23rd Jun 2022, 7:07 am | #23 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Carriba!.
Thanks Mike. If i do go that route might source some proper ones from Dada -possibly why i have some spare new ones. I think that is what i did before on another 303 i built with new boards from China some years back - similar to that old thread - possibly ten years now. No access to a scope unfortunately only multimeter. I should have mentioned - brain fog - once switched on for the first time in the day it doesn't pop on subsequent turn on during the day unless left off for some time - would that point to capacitor charging up for the first time and then depleting if left off for a period of time? I did post this on the FB Quad group and suggestion is to go over all the joints on the board and re-solder so a job for the weekend. Last edited by mikes08; 23rd Jun 2022 at 7:14 am. |
27th Jun 2022, 1:25 pm | #24 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
I reflowed the joints over weekend and no joy so swapped out Tr102 (ZTX304) for a BC546 but was getting some strange voltages (39v instead of 67v across pins 1 and 9 on the board) so swapped back again - voltages normal again. I am looking at two data sheets for the ZTX300 series which show the Emitter and collector transposed so may have fitted the BC546 wrong way round unless the sun got to me over the weekend?
Quiescent all good. Diodes all good. Does anyone have a definitive configuration - I do tend to go with 'alldatasheet' but it might be wrong? If that doesn't solve it going to swap out the two power transistors (with genuine RCA spares i have from another 303) as definitely confirmed only right channel affected. https://alltransistors.com/adv/pdfvi...f&dire=_diodes https://pdf1.alldatasheet.com/datash...LA/BC546B.html I could try swapping the boards over and then if the pop stayed in the right channel i know the boards are not at fault. Last edited by mikes08; 27th Jun 2022 at 1:35 pm. |
27th Jun 2022, 1:39 pm | #25 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 201
|
Re: Quad 303 pop on switch on
Alldata is correct. I wouldn't swap out the power transistors.
__________________
Pete BVWS Member |
27th Jun 2022, 1:46 pm | #26 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
|
27th Jun 2022, 1:47 pm | #27 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,580
|
Re: Quad 303 pop on switch on
You need to swap the EC connections over. Always check data sheets when swapping transistors. Some have emitter in the centre, most have collector in the centre but a lot of the 'BC' range have base in the centre. I did a similar thing with an old Akai amp when subbing the pre-drivers. Just had to be careful when using BC638's making sure they were inserted correctly. A transistor data book is invaluable.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
27th Jun 2022, 1:55 pm | #28 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Many thanks - I have the circuit diagram so will double check the right legs go the right components on the board first. At least base is the same so i might have 'inverted' it. I have done it before and a quick swap round sorted it
|
27th Jun 2022, 1:58 pm | #29 |
Pentode
Join Date: Feb 2020
Location: Waterlooville, Hampshire, UK.
Posts: 201
|
Re: Quad 303 pop on switch on
If, after swapping the EC connections over you still have the fault it is far easier to swap the boards over (18 connections) than to remove the heatsink and faff around replacing the output transistors. I would view this as a last resort after thoroughly investigating the board.
__________________
Pete BVWS Member |
27th Jun 2022, 4:33 pm | #30 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Thanks Pete.
I know what you are saying. I have done one before on a 303 when i re-built one but will start with the easy option first and eliminate the boards as a source of the problem. |
27th Jun 2022, 4:52 pm | #31 |
Dekatron
Join Date: Jul 2008
Location: Kington, Herefordshire, UK.
Posts: 3,675
|
Re: Quad 303 pop on switch on
Could this be momentary instability? Are the output transistors to spec?
|
30th Jun 2022, 7:19 am | #32 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Replaced TR 102 and no change so next is to swap the boards over and if the 'pop' stays in the right channel will investigate the output transistors.
|
3rd Jul 2022, 8:47 am | #33 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Swapped the boards over yesterday and the 'pop' on turn on remains in the right channel which leads me to think the problem lies with the power transistors - right channel are the top two on the heatsink. I have two spare RCA ones which i saved from another 303 when i rebuilt that with modern boards and changed all five TR's on the heatsink with those supplied from Dada so that is my next plan. I have had a meter on them in diode mode and the readings don't look amiss but i guess as switched on one could go wobbly?
As stated the amp works fine once switched on. The main capacitors were all changed from the recent Dada kit upgrade but i suppose it is not impossible one of those could be faulty from new. Anywhere else i could look? KR Mike |
3rd Jul 2022, 8:57 am | #34 |
Dekatron
Join Date: Sep 2011
Location: Rugeley, Staffordshire, UK.
Posts: 8,835
|
Re: Quad 303 pop on switch on
I fitted a brand new faulty cap to a wireless just a few months ago, it happens.
__________________
A digital radio is the latest thing, but a vintage wireless is forever.. |
3rd Jul 2022, 9:11 am | #35 |
Hexode
Join Date: Mar 2014
Location: Peacehaven, East Sussex, UK.
Posts: 278
|
Re: Quad 303 pop on switch on
I would try swapping the output capacitors over
|
3rd Jul 2022, 9:13 am | #36 | |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
Quote:
I could swap those left to right and see if the problems migrates - ten minute job. Going forward can anyone suggest a reasonable transistor tester that would be worth purchasing? Alternatively a second hand oscilloscope though would have to learn how to use? Last edited by mikes08; 3rd Jul 2022 at 9:31 am. |
|
3rd Jul 2022, 10:18 am | #37 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
|
Re: Quad 303 pop on switch on
I use one of these and found out that the transistors go low gain / nsy with age https://www.peakelec.co.uk/acatalog/...-analyser.html
__________________
Any tool can be used as a hammer but a screwdriver makes the best chisel |
3rd Jul 2022, 11:41 am | #38 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,996
|
Re: Quad 303 pop on switch on
Peak are a great company. I used a DCA55, but eventually bought a DCA75, which does curve tracing too. Out of stock alas, although the DCA55 is in stock.
Craig
__________________
Doomed for a certain term to walk the night |
3rd Jul 2022, 3:32 pm | #39 |
Pentode
Join Date: Dec 2021
Location: Canterbury, Kent, UK.
Posts: 135
|
Re: Quad 303 pop on switch on
How odd! I swapped the output capacitors over (Epos 10,000mf from Dada) and hey presto, the pop on turning on had migrated to the left channel. Yes I thought, might have a dodgy capacitor after all so i swapped both out for some new spare Denon 12,000mf capacitors i had but not used previously.
Oh poop - the pop is still in the left channel on turn on. What am i missing please? |
3rd Jul 2022, 4:13 pm | #40 |
Nonode
Join Date: Mar 2005
Location: Nuneaton, Warwickshire, UK.
Posts: 2,039
|
Re: Quad 303 pop on switch on
Dodgy Denon cap? Try swapping those around perhaps?
Aub
__________________
Life's a long song, but the tune ends too soon for us all. |