Quad 11 Problem. - UK Vintage Radio Repair and Restoration Discussion Forum

sparkymike · 2nd Dec 2019, 6:46 pm

My Quad 11 valve set up is lacking in bass. I am wondering if anything in the preamp could cause this ?
Mike.

Herald1360 · 2nd Dec 2019, 7:12 pm

Short answer is "Yes", but that's hardly much use to you.

If there's plenty of bass if you drive the Quad II directly from a flat source, then your problem is probably in the preamp. Are you using the right plugin for whatever your signal sources are? Is it a new problem in a system that's been fine or is the system or part of it at least new to you? Is the preamp a QC2 or a 22 or a "foreigner"?

sparkymike · 2nd Dec 2019, 10:19 pm

The preamp is a 22. Had them since the mid 60's, sold them to a German friend in the 80's and bought them back in the 2000's !! You have a point about the adaptors. Will check if they are fitted. I am running a Lenco/Goldring GL75 deck with standard cartridge. (Shure M75 MB)
Come to think of it, the three equlliser buttons do not make any effect on the tone.
Mike.

sparkymike · 3rd Dec 2019, 1:56 pm

I removed the phono adaptor and found that the pins were all tarnished, almost black, so I will see if there is an improvement now they are a great deal cleaner.
I am surprised that any signal got through after looking at them at first.
I looked on Keith Snook's site and found a lot of very useful info on the 22 preamp. In fact he mentions to check the EF86 for quality, as that can reduce the bass. I will progress systematically and try it after each check.
Mike.

sparkymike · 3rd Dec 2019, 5:44 pm

Now found that the R 18 and R 19 resistors are high, (one very high or o/c), so need to change them and one of the linked caps has gone high, but as they are both Hunts type, have changed both. Further work will have to wait until I get the resistors.
This is first time any work has been done on this preamp, since it was checked over by the late John Cox in Ipswich.
Mike.

GrimJosef · 3rd Dec 2019, 6:24 pm

I'm afraid these are fiddly to work on. The case was originally sized for the mono QC II. It was traditionally mounted in a wooden panel forming part of the overall system's cabinet. When stereo became popular Quad seem to have decided to stick with the same-sized case for the new 22 control unit. This had the advantage that customers could simply slide the QC II out and drop the 22 into the existing hole, without having to do any woodwork. The disadvantage of course is that with nearly twice as many components the 22 was very crowded inside. Some parts restrict access to other parts. And many of the small Hunts capacitors are prone to degrading, including drifting in value. Since they are in frequency-tuned circuits this matters. If you find you have to do much work on this unit then you have my sympathies ...

Cheers,

GJ

sparkymike · 3rd Dec 2019, 10:14 pm

Hi CJ,
I just realised that I had put a similar post on the forum several years ago and came across it by accident while searching for info about the 22 preamp !!
The lack of bass is now to the effect that the bass control has to be rotated to full on and the treble the opposite way.
Now that I am having a fresh go at this, I will check all the components this time and see what I can find. I did swap the two EF86 valves to see if this made any change ,but no.( I am only using one channel, so at the moment the other is redundant.)
Mike.

sparkymike · 4th Dec 2019, 6:30 pm

Have now checked out all the resistors ,bar two which I can't find, R10 and R11.
Most are close to original. Only ones which are not are R4 4.7K reading 6K.
R6 15K reading 20.6K , R18 1.5 Meg reading 3.7Meg, R19 1.5 Meg reading o/c R30 47K reading 73 K, R31 47K reading 124K, R39 330K reading 362K,
Should I replace all the above, or would some of these not make much difference to the set ?
Mike.

sparkymike · 5th Dec 2019, 5:02 pm

I have now replaced R18 and R19 to no effect. The sound, as best as I can describe it, is something like a cheap transistor radio, with nearly ,(not quite), a total loss of bass. Another clue, to those much more learned than me on this set, is that none of the tone/equaliser rotary or push button controls have any effect on the sound. Bass control works in that you can hear a slight change of bass from one end of the pot to the other. If I had some old type headphones, I could work back through the circuit. Not sure if I could use my Senheiser HD 450,s? Any help here would be welcome .I don't want to give up this time!!
Mike.

thermionic · 6th Dec 2019, 8:06 am

Hi Mike.

You will need to check all the capacitors associated with the tone control circuitry. These components are mounted close to the controls themselves. The small capacitors will all be faulty, if they have not already been replaced.

Some types fitted look like torpedo shaped resistors, others are red Hunts. These are all worth checking for leakage and capacity. If you haven’t done so already, then the remaining capacitors must be checked as well.

Don’t forget the carbon composition resistors too! These tend to drift with age and temperature.

Good luck!

SimonT.

John Caswell · 6th Dec 2019, 10:06 am

I have just overhauled 3 QC22 preamps, and every capacitor in them was either o/c or high as per SimonT's comments plus many of the resistors as well as the switch suppressors were well out of tolerance or u/s. They are somewhat difficult to work on.

John

sparkymike · 7th Dec 2019, 9:15 am

Thanks John,
yes they are next items to check out/replace. They are the usual Hunts type caps. I ordered on line some replacement resistors and although size was comparable, the lead out wires were not much thicker than a human hair.
Any idea where I can get more suitable look-alike types that don't look out of place.?

GrimJosef · 7th Dec 2019, 9:49 am

Rapid Online do a few new-production carbon compositions which look the part https://www.rapidonline.com/Carbon-Composition. HiFi Collective do the same resistors at a higher price but cover a much wider range of values https://www.hificollective.co.uk/com...resistors.html. RS sell them too, at an intermediate price, but there is a minimum order of 25 of each value I think. They're marked as 5% tolerance but I don't know whether their long-term stability is any better than the original ones (then again maybe you're not looking at performance on a 60-year timescale). They'll be noisier than carbon films (much better) or metal films (best).

Cheers,

GJ

Craig Sawyers · 7th Dec 2019, 11:10 am

Farnell have a wide range of values too in smaller pack sizes than RS, of 5 off. But for one off values the most cost effective way is hificollective as GJ mentions.

There have already been a couple of obvious replacements already - the two yellow tubular caps on the right hand side look like new parts.

But apart from wildly out of tolerace resistors, the black tubular Hunts caps will absolutely be toast - either with a low resistance, or hardly any capacitance, or both of those.

Leave any other capacitors alone - the polystyrenes will absolutely be OK.

ahankinson · 7th Dec 2019, 12:30 pm

What's the status of the amps themselves? Have the coupling caps (C2/C3) been replaced, or are they still original? I haven't experienced it myself, but having read others' stories, when they go, they may take out the valve and possibly the output transformers. It's worth replacing them as a matter of course.

Since the rectifier for the Q22 is in the amplifiers, it's worth having a look at the GZ32 to see if the voltages coming out of the amp back to the preamp are in spec. There should be about 330v on pin 3 of the six pin socket on the amp.

For the 22 preamp, C5/C6 and C10/C11 are 22µF electrolytics, so they should be suspected of being dried out and checked. You can also try to do the capacitors in the can, but it's really hard to disentangle everything.

Have you checked voltages against the schematic?

You may have seen it, but in case you haven't the annotated images for the underside and the top side done by Keith Snook are invaluable for working on these.

GrimJosef · 7th Dec 2019, 2:30 pm

Quote:

Originally Posted by ahankinson

... it's worth having a look at the GZ32 to see if the voltages coming out of the amp back to the preamp are in spec. There should be about 330v on pin 3 of the six pin socket on the amp ...

Actually more like 360V with a GZ32 or 370V with a GZ34, depending on the state of the valve and the local mains voltage. The circuit diagram that Quad supplied free with the Quad II handbook had a lower value for this voltage printed on it. But it just seems to be a mistake.

Cheers,

GJ

sparkymike · 7th Dec 2019, 4:15 pm

I will check the preamp output voltage on jones plug.
All four of the 25uf electolytics are wildly out of spec so they will be first for the chop. If I can get some same size, they should be fairly simple to change.
Thanks for all input so far gents, all good useful help.
Mike.

sparkymike · 7th Dec 2019, 8:45 pm

HT voltage is 362 and the rectifier is a Mullard GZ 32.
Mike.

GrimJosef · 7th Dec 2019, 8:48 pm

Sounds like it's spot on.

Cheers,

GJ

sparkymike · 7th Dec 2019, 9:23 pm

Hi CJ, That was a relief, seeing that voltage on the meter. I might as well check the volts from one end of the preamp to the other and I will check the output voltages as well. An early spring clean so to speak !
Over the years it has given good service and has enabled me to hear the music as it should sound. Volume is not the be all and end all, I probably have only used this up to position 3 on the volume control.
Mike.

2nd Dec 2019, 6:46 pm	#1
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Quad 11 Problem. My Quad 11 valve set up is lacking in bass. I am wondering if anything in the preamp could cause this ? Mike.

2nd Dec 2019, 7:12 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Quad 11 Problem. Short answer is "Yes", but that's hardly much use to you. If there's plenty of bass if you drive the Quad II directly from a flat source, then your problem is probably in the preamp. Are you using the right plugin for whatever your signal sources are? Is it a new problem in a system that's been fine or is the system or part of it at least new to you? Is the preamp a QC2 or a 22 or a "foreigner"? __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

2nd Dec 2019, 10:19 pm	#3
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. The preamp is a 22. Had them since the mid 60's, sold them to a German friend in the 80's and bought them back in the 2000's !! You have a point about the adaptors. Will check if they are fitted. I am running a Lenco/Goldring GL75 deck with standard cartridge. (Shure M75 MB) Come to think of it, the three equlliser buttons do not make any effect on the tone. Mike.

3rd Dec 2019, 1:56 pm	#4
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. I removed the phono adaptor and found that the pins were all tarnished, almost black, so I will see if there is an improvement now they are a great deal cleaner. I am surprised that any signal got through after looking at them at first. I looked on Keith Snook's site and found a lot of very useful info on the 22 preamp. In fact he mentions to check the EF86 for quality, as that can reduce the bass. I will progress systematically and try it after each check. Mike.

3rd Dec 2019, 5:44 pm	#5
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. Now found that the R 18 and R 19 resistors are high, (one very high or o/c), so need to change them and one of the linked caps has gone high, but as they are both Hunts type, have changed both. Further work will have to wait until I get the resistors. This is first time any work has been done on this preamp, since it was checked over by the late John Cox in Ipswich. Mike.

3rd Dec 2019, 6:24 pm	#6
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Quad 11 Problem. I'm afraid these are fiddly to work on. The case was originally sized for the mono QC II. It was traditionally mounted in a wooden panel forming part of the overall system's cabinet. When stereo became popular Quad seem to have decided to stick with the same-sized case for the new 22 control unit. This had the advantage that customers could simply slide the QC II out and drop the 22 into the existing hole, without having to do any woodwork. The disadvantage of course is that with nearly twice as many components the 22 was very crowded inside. Some parts restrict access to other parts. And many of the small Hunts capacitors are prone to degrading, including drifting in value. Since they are in frequency-tuned circuits this matters. If you find you have to do much work on this unit then you have my sympathies ... Cheers, GJ __________________ http://www.ampregen.com

3rd Dec 2019, 10:14 pm	#7
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. Hi CJ, I just realised that I had put a similar post on the forum several years ago and came across it by accident while searching for info about the 22 preamp !! The lack of bass is now to the effect that the bass control has to be rotated to full on and the treble the opposite way. Now that I am having a fresh go at this, I will check all the components this time and see what I can find. I did swap the two EF86 valves to see if this made any change ,but no.( I am only using one channel, so at the moment the other is redundant.) Mike.

4th Dec 2019, 6:30 pm	#8
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. Have now checked out all the resistors ,bar two which I can't find, R10 and R11. Most are close to original. Only ones which are not are R4 4.7K reading 6K. R6 15K reading 20.6K , R18 1.5 Meg reading 3.7Meg, R19 1.5 Meg reading o/c R30 47K reading 73 K, R31 47K reading 124K, R39 330K reading 362K, Should I replace all the above, or would some of these not make much difference to the set ? Mike.

5th Dec 2019, 5:02 pm	#9
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. I have now replaced R18 and R19 to no effect. The sound, as best as I can describe it, is something like a cheap transistor radio, with nearly ,(not quite), a total loss of bass. Another clue, to those much more learned than me on this set, is that none of the tone/equaliser rotary or push button controls have any effect on the sound. Bass control works in that you can hear a slight change of bass from one end of the pot to the other. If I had some old type headphones, I could work back through the circuit. Not sure if I could use my Senheiser HD 450,s? Any help here would be welcome .I don't want to give up this time!! Mike.

6th Dec 2019, 8:06 am	#10
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 988	Re: Quad 11 Problem. Hi Mike. You will need to check all the capacitors associated with the tone control circuitry. These components are mounted close to the controls themselves. The small capacitors will all be faulty, if they have not already been replaced. Some types fitted look like torpedo shaped resistors, others are red Hunts. These are all worth checking for leakage and capacity. If you haven’t done so already, then the remaining capacitors must be checked as well. Don’t forget the carbon composition resistors too! These tend to drift with age and temperature. Good luck! SimonT. __________________ The honesty of imperfection..........

6th Dec 2019, 10:06 am	#11
John Caswell Hexode Join Date: Jul 2009 Location: Wokingham, Berkshire, UK. Posts: 437	Re: Quad 11 Problem. I have just overhauled 3 QC22 preamps, and every capacitor in them was either o/c or high as per SimonT's comments plus many of the resistors as well as the switch suppressors were well out of tolerance or u/s. They are somewhat difficult to work on. John

7th Dec 2019, 9:15 am	#12
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. Thanks John, yes they are next items to check out/replace. They are the usual Hunts type caps. I ordered on line some replacement resistors and although size was comparable, the lead out wires were not much thicker than a human hair. Any idea where I can get more suitable look-alike types that don't look out of place.? Attached Thumbnails

7th Dec 2019, 9:49 am	#13
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Quad 11 Problem. Rapid Online do a few new-production carbon compositions which look the part https://www.rapidonline.com/Carbon-Composition. HiFi Collective do the same resistors at a higher price but cover a much wider range of values https://www.hificollective.co.uk/com...resistors.html. RS sell them too, at an intermediate price, but there is a minimum order of 25 of each value I think. They're marked as 5% tolerance but I don't know whether their long-term stability is any better than the original ones (then again maybe you're not looking at performance on a 60-year timescale). They'll be noisier than carbon films (much better) or metal films (best). Cheers, GJ __________________ http://www.ampregen.com

7th Dec 2019, 11:10 am	#14
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,980	Re: Quad 11 Problem. Farnell have a wide range of values too in smaller pack sizes than RS, of 5 off. But for one off values the most cost effective way is hificollective as GJ mentions. There have already been a couple of obvious replacements already - the two yellow tubular caps on the right hand side look like new parts. But apart from wildly out of tolerace resistors, the black tubular Hunts caps will absolutely be toast - either with a low resistance, or hardly any capacitance, or both of those. Leave any other capacitors alone - the polystyrenes will absolutely be OK.

7th Dec 2019, 12:30 pm	#15
ahankinson Triode Join Date: Sep 2016 Location: Banbury, Oxon, UK. Posts: 33	Re: Quad 11 Problem. What's the status of the amps themselves? Have the coupling caps (C2/C3) been replaced, or are they still original? I haven't experienced it myself, but having read others' stories, when they go, they may take out the valve and possibly the output transformers. It's worth replacing them as a matter of course. Since the rectifier for the Q22 is in the amplifiers, it's worth having a look at the GZ32 to see if the voltages coming out of the amp back to the preamp are in spec. There should be about 330v on pin 3 of the six pin socket on the amp. For the 22 preamp, C5/C6 and C10/C11 are 22µF electrolytics, so they should be suspected of being dried out and checked. You can also try to do the capacitors in the can, but it's really hard to disentangle everything. Have you checked voltages against the schematic? You may have seen it, but in case you haven't the annotated images for the underside and the top side done by Keith Snook are invaluable for working on these.

7th Dec 2019, 4:15 pm	#17
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. I will check the preamp output voltage on jones plug. All four of the 25uf electolytics are wildly out of spec so they will be first for the chop. If I can get some same size, they should be fairly simple to change. Thanks for all input so far gents, all good useful help. Mike.

7th Dec 2019, 8:45 pm	#18
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. HT voltage is 362 and the rectifier is a Mullard GZ 32. Mike.

7th Dec 2019, 8:48 pm	#19
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Quad 11 Problem. Sounds like it's spot on. Cheers, GJ __________________ http://www.ampregen.com

7th Dec 2019, 9:23 pm	#20
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 Problem. Hi CJ, That was a relief, seeing that voltage on the meter. I might as well check the volts from one end of the preamp to the other and I will check the output voltages as well. An early spring clean so to speak ! Over the years it has given good service and has enabled me to hear the music as it should sound. Volume is not the be all and end all, I probably have only used this up to position 3 on the volume control. Mike.