|
Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
|
Thread Tools |
28th Jan 2023, 8:06 pm | #1 |
Diode
Join Date: Jan 2023
Location: Folkestone Kent
Posts: 5
|
Hacker Gondalier GP42 - servicing amp
Hi - new member, first post.
I have purchased a Hacker GP42 to restore, this being only the second record player I have restored. Would consider myself competent with a soldering iron and meter, but a novice at valve technology (and most other electronic circuitry). Have serviced the deck and have run the amp using a digital radio as input - it sounds really good with no distortion. Where I need some help is in establishing whether I should be replacing any components whilst I have the unit apart. I have used https://www.vintage-radio.net/forum/...d.php?t=111739 as a tutorial and have checked all the resistors and the three key voltages. 1) 7 of the resistors are more than 20% out of tolerance (R1, R4, R7, R8, R9, R11, R12). Should I replace these, and what difference should I expect in performance if I do so (or will the amp likely fail in the near future if I don't?) 2) measured voltage across C8 at 235.5v, C11 £279.1v and C12 £263.8v on DMM. Presumably these are all close enough to spec? 3) DO I need to replace any of the capacitors or can I safely leave alone? Many thanks |
29th Jan 2023, 1:41 pm | #2 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
|
Re: Hacker Gondalier GP42 - servicing amp
If it "sounds really good with no distortion" then why faff about with it? You may have read much about the "need" to change capacitors. Yes, there are key mains and coupling caps that may need attention in due course, but for now leave well alone!
__________________
Edward. |
1st Feb 2023, 9:29 am | #3 |
Nonode
Join Date: Nov 2016
Location: Aberaeron, Ceredigion, Wales, UK.
Posts: 2,869
|
Re: Hacker Gondalier GP42 - servicing amp
The tutorial you refer to is very informative, and as stated the capacitors are considered very reliable. You say there is no distortion and it sounds ok, also your voltage readings, using your DMM are close enough, the original voltage reading were taken using AVO meter. So I would agree with Edward.
John |
1st Feb 2023, 11:21 am | #4 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
|
Re: Hacker Gondalier GP42 - servicing amp
Could we have a clearer picture, please, Martin?
The coupling capacitors we're especially interested in are just blurry red blobs in your original image If it were mine, I would replace these two capacitors as a matter of course, and then leave well alone as Edward suggests. |
1st Feb 2023, 12:39 pm | #5 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
|
Re: Hacker Gondalier GP42 - servicing amp
How far you want to go with restoration depends on how often you plan to use it. If you will be using it regularly I would replace the out of tolerance resistors and capacitors.
|
2nd Feb 2023, 10:47 am | #6 |
Moderator
Join Date: Feb 2006
Location: Wembley, Middlesex
Posts: 7,219
|
Re: Hacker Gondalier GP42 - servicing amp
All the GP42's I've seen have had Mullard mustard coupling capacitors which should be fine. I replace the two 220K resistors on the top tag strip together with the 220R, 2.2K on the bottom tag strip and the 4 47uF electrolytic capacitors.
|
6th Feb 2023, 10:00 am | #7 |
Diode
Join Date: Jan 2023
Location: Folkestone Kent
Posts: 5
|
Re: Hacker Gondalier GP42 - servicing amp
|
6th Feb 2023, 10:30 am | #8 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
|
Re: Hacker Gondalier GP42 - servicing amp
That's much better!
Michael, what do you think? Are those the Mullards you were referring to? They certainly look like their C296 "mustards", albeit bright red. |
6th Feb 2023, 7:26 pm | #9 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
|
Re: Hacker Gondalier GP42 - servicing amp
The one with visible text has LEMCO on it so not Mullard Mustards.
If they're plastic film types they should be OK. Not sure those resistors look original? Has anyone been at it already?
__________________
....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
6th Feb 2023, 8:47 pm | #10 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Hacker Gondalier GP42 - servicing amp
That's what I thought, five band resistors. The soldering on the Lemco capacitors looks original though.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
6th Feb 2023, 9:26 pm | #11 |
Diode
Join Date: Jan 2023
Location: Folkestone Kent
Posts: 5
|
Re: Hacker Gondalier GP42 - servicing amp
I replaced the resistors last week! Am inclined to leave the rest alone as it’s working well.
Thanks all for your help. |