Quad 34 Problems - UK Vintage Radio Repair and Restoration Discussion Forum

valveaudio · 27th Oct 2009, 6:08 pm

I am not sure if this should in the vintage or modern section. Mods please move it if you think it is wrong.

I have been working on a Quad 34 and have a problem with the filter switching. I cannot get F1 to work unless F2 has previously been selected. Pressing F1 without F2 pressed does not operate the latch which in turn operates the associated analog switches.

I have a schematic and have tried replacing the 4013 latches and have tested all the associated components, all seem to be OK.

Has anyone seen this problem, I would love to hear from you.

Trevor

percival007 · 27th Oct 2009, 8:10 pm

Hi,

i posted a thread asking for help on this unit and got some great replies but i can't find it any longer.

If i remember correctly, check for leaking caps on the main pcb which have leaked thier innards on to the track and corroded it. You have to remove the caps to see the damage i think and i would replace all of the electrolytics if i were you.

I wish i could find the thread but it has gone, i found this thread which has a post from me detailing the thread i mean but this link no longer works?!?!?

https://www.vintage-radio.net/forum/...ad.php?t=38681

Can the mods look into this?

All the best,

James.

audiomm · 28th Oct 2009, 8:54 pm

Quote:

Originally Posted by valveaudio

I am not sure if this should in the vintage or modern section. Mods please move it if you think it is wrong.

I have been working on a Quad 34 and have a problem with the filter switching. I cannot get F1 to work unless F2 has previously been selected. Pressing F1 without F2 pressed does not operate the latch which in turn operates the associated analog switches.

I have a schematic and have tried replacing the 4013 latches and have tested all the associated components, all seem to be OK.

Has anyone seen this problem, I would love to hear from you.

Trevor

Replace the two 4066's (IC17 & IC18) as one or both of these is likely faulty.
Also consider that the latching switch itself could faulty but I'd replace those IC's first.

Mike Phelan · 29th Oct 2009, 10:00 am

Have a close look at the top side of the print in this area, especially any tracks that pass near electrolytics.
They can leak goo and corrode the print - the same symptom as yours happened to me a while ago on a 34 and took a while to find the reason.

valveaudio · 2nd Nov 2009, 4:48 pm

Thanks

Replaced the electrolytics and at the same time cleaned and bridged the corroded tracks but still no F1 switching. Replaced R98 (10M) it seemed to be intermittently high. Everything now OK
Trevor

Mike Phelan · 2nd Nov 2009, 5:57 pm

Good result, Trevor. Any 10M resistor is a candidate for suspicion! So, there was corrosion on the print, then. It's becoming a stock fault.

27th Oct 2009, 6:08 pm	#1
valveaudio Hexode Join Date: Feb 2006 Location: Diss, Norfolk, UK. Posts: 386	Quad 34 Problems I am not sure if this should in the vintage or modern section. Mods please move it if you think it is wrong. I have been working on a Quad 34 and have a problem with the filter switching. I cannot get F1 to work unless F2 has previously been selected. Pressing F1 without F2 pressed does not operate the latch which in turn operates the associated analog switches. I have a schematic and have tried replacing the 4013 latches and have tested all the associated components, all seem to be OK. Has anyone seen this problem, I would love to hear from you. Trevor

27th Oct 2009, 8:10 pm	#2
percival007 Heptode Join Date: May 2005 Location: Oxfordshire, UK. Posts: 852	Re: Quad 34 Problems Hi, i posted a thread asking for help on this unit and got some great replies but i can't find it any longer. If i remember correctly, check for leaking caps on the main pcb which have leaked thier innards on to the track and corroded it. You have to remove the caps to see the damage i think and i would replace all of the electrolytics if i were you. I wish i could find the thread but it has gone, i found this thread which has a post from me detailing the thread i mean but this link no longer works?!?!? https://www.vintage-radio.net/forum/...ad.php?t=38681 Can the mods look into this? All the best, James.

29th Oct 2009, 10:00 am	#4
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Quad 34 Problems Have a close look at the top side of the print in this area, especially any tracks that pass near electrolytics. They can leak goo and corrode the print - the same symptom as yours happened to me a while ago on a 34 and took a while to find the reason. __________________ Mike.

2nd Nov 2009, 4:48 pm	#5
valveaudio Hexode Join Date: Feb 2006 Location: Diss, Norfolk, UK. Posts: 386	Re: Quad 34 Problems Thanks Replaced the electrolytics and at the same time cleaned and bridged the corroded tracks but still no F1 switching. Replaced R98 (10M) it seemed to be intermittently high. Everything now OK Trevor

2nd Nov 2009, 5:57 pm	#6
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Quad 34 Problems Good result, Trevor. Any 10M resistor is a candidate for suspicion! So, there was corrosion on the print, then. It's becoming a stock fault. __________________ Mike.