Quad II test run. - Page 9 - UK Vintage Radio Repair and Restoration Discussion Forum

sparkymike · 8th Apr 2020, 6:39 am

PJL
W goes to pin 8 on valve next to mains transformer. (valve 4 ?)
U goes to pin 8 on valve next to tag board. (valve 3 ?)
Mike.

PJL · 8th Apr 2020, 10:08 am

X and W go to V6 (trader) next to mains transformer
Y and U go to V5 (trader)
So all is correct according to the trader.

Unless anyone thinks differently we appear to be ready to try the amp with W and U reversed. Did you make that change to the internal transformer connections?

Connect your scope up to turret W with earth to chassis.
Connect your DMM to chassis and turret V.
Connect your dummy load.
Switch on and be ready to switch off quickly.
Monitor the DMM and make sure it starts to rise.
Monitor the scope looking for oscillation, switch off immediately if it does oscillate.
Switch off if the voltage on V exceeds 26V.

sparkymike · 8th Apr 2020, 11:09 am

Hi PJL,
W and U not changed over yet, as I am trying to get dark blue flaky gloss paint off a wall which I have been ordered by WF to paint !! I will resume later today pm (I hope).
Mike.

sparkymike · 10th Apr 2020, 8:25 am

Right, household chores took over, but now back again.

Windings U and W now changed over inside OPT. Connected up the patient and voltage held at 30 volts DC. Little more than you said, but output voltage from rectifier is a bit on the high side, which may account for that. Scope trace is just a wide blur/mush. One other thing, when I switch off there is a slight squark from the speaker, although hum level seems to be reduced somewhat. Feedback still disconnected.

Mike.

PJL · 10th Apr 2020, 9:25 am

Doesn't look good as the wide blur/mush sounds like instability. Don't leave it powered up for more than a few minutes.

What happens if you remove the feedback? Do you also have a working Quad II?

Ted Kendall · 10th Apr 2020, 9:39 am

The chirrup on switch-off is a dead giveaway, too - something's squawking.

sparkymike · 10th Apr 2020, 9:49 am

Yes I do have one working Quad II.
Mike.

PJL · 10th Apr 2020, 12:03 pm

I would remove the valves from both, check they are both set to 15 ohms and on the same mains voltage selection, and wire both up with the link to the heater winding.

You can then do a comparison of phase and amplitude at each turret between the good and bad chassis as we (you) did before. You could also include a more accurate measure of AC volts on each turret using your DMM.

This way you can eliminate any issues that might occur from using different test equipment or procedure to GJ.

Did you check the U/S marked EF86 base?

sparkymike · 11th Apr 2020, 9:12 am

Hi PJL,
The EF86 valve base I have checked briefly for low resistance but will look at it more closely today with a bit of luck.
I will use my good Quad for comparing the various voltages and traces with the other one. I might just buy another OPT from Majestic anyway (if they still make them) , as if I found that I did not need it, I could always keep it for a spare for either amp, or even sell it on the auction site.
Mike.

sparkymike · 11th Apr 2020, 11:54 am

I am checking out the valve bases and so far anode to earth is around 10 meg on both. Now I find that pin 2 on each valve connects to 2 on the Jones plug.
This does not seem correct to the original quad circuit diagram ? On drawing, EF86 next to Jones plug does go direct, but the other connects with R8.??
Mike.

snowman_al · 11th Apr 2020, 1:45 pm

Quote:

Originally Posted by sparkymike

... This does not seem correct to the original quad circuit diagram ? On drawing, EF86 next to Jones plug does go direct, but the other connects with R8.??
Mike.

That is an error in your wiring. If that is the case there is no phase inversion for the lower EF86 (V2). The correct feed to the V2 grid is from the divider network R7, R8 and R9 which is 180 degrees out of phase (ie inverted) from the input to V1. Does anything on your amp connect to the junction of R8 and R7?

Quote:

Originally Posted by sparkymike

I am checking out the valve bases and so far anode to earth is around 10 meg on both. Now I find that pin 2 on each valve connects to 2 on the Jones plug.

I would check for loose grip of the valve pins first...

snowman_al · 11th Apr 2020, 2:28 pm

Oops.
Line one should have read

Quote:

Originally Posted by sparkymike

...Now I find that pin 2 on each valve connects to 2 on the Jones plug. This does not seem correct to the original quad circuit diagram ? On drawing, EF86 next to Jones plug does go direct, but the other connects with R8.??

That is an error in your wiring. If that is the case there is no phase inversion for the lower EF86 (V2). The correct feed to the V2 grid is from the divider network R7, R8 and R9 which is 180 degrees out of phase (ie inverted) from the input to V1. Does anything on your amp connect to the junction of R8 and R7?

sparkymike · 11th Apr 2020, 2:35 pm

"That is an error in your wiring."
I hasten to add, not exactly my wiring as the tag board and loom came to me in one piece which I assumed, (now wrongly)an original quad loom and board.
Will compare all this part of the amp with the good Quad.
Mike.

sparkymike · 11th Apr 2020, 3:29 pm

Well the original, since early 64, to me, working Quad is wired in exactly the same way. So what is going on here, is the Quad drawing incorrect ?
Keith Snook has re-drawn the original circuit and went to his site, but could not get in due to out of date certification of site.
Mike.

sparkymike · 11th Apr 2020, 3:49 pm

Solved that small mystery. Pin 2 is a screen and as such does not show up on the Quad original drawing.
Mike.

snowman_al · 11th Apr 2020, 4:36 pm

Quote:

Originally Posted by sparkymike

Solved that small mystery. Pin 2 is a screen and as such does not show up on the Quad original drawing.
Mike.

Yep you are correct. I should have checked the pin outs of an EF86...
Pin 9 is the input grid, doh.

Quote:

Originally Posted by sparkymike

...I hasten to add, not exactly my wiring as the tag board and loom came to me in one piece

Did not imply you had done it, just that what you had was wrong. As it happens I was and not the board.
Back under my rock then, Alan

8th Apr 2020, 6:39 am	#161
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad 11 test run PJL W goes to pin 8 on valve next to mains transformer. (valve 4 ?) U goes to pin 8 on valve next to tag board. (valve 3 ?) Mike.

8th Apr 2020, 10:08 am	#162
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Quad II test run X and W go to V6 (trader) next to mains transformer Y and U go to V5 (trader) So all is correct according to the trader. Unless anyone thinks differently we appear to be ready to try the amp with W and U reversed. Did you make that change to the internal transformer connections? Connect your scope up to turret W with earth to chassis. Connect your DMM to chassis and turret V. Connect your dummy load. Switch on and be ready to switch off quickly. Monitor the DMM and make sure it starts to rise. Monitor the scope looking for oscillation, switch off immediately if it does oscillate. Switch off if the voltage on V exceeds 26V. Last edited by PJL; 8th Apr 2020 at 10:19 am.

8th Apr 2020, 11:09 am	#163
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Hi PJL, W and U not changed over yet, as I am trying to get dark blue flaky gloss paint off a wall which I have been ordered by WF to paint !! I will resume later today pm (I hope). Mike.

10th Apr 2020, 8:25 am	#164
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Right, household chores took over, but now back again. Windings U and W now changed over inside OPT. Connected up the patient and voltage held at 30 volts DC. Little more than you said, but output voltage from rectifier is a bit on the high side, which may account for that. Scope trace is just a wide blur/mush. One other thing, when I switch off there is a slight squark from the speaker, although hum level seems to be reduced somewhat. Feedback still disconnected. Mike.

10th Apr 2020, 9:25 am	#165
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Quad II test run. Doesn't look good as the wide blur/mush sounds like instability. Don't leave it powered up for more than a few minutes. What happens if you remove the feedback? Do you also have a working Quad II?

10th Apr 2020, 9:39 am	#166
Ted Kendall Dekatron Join Date: Jul 2008 Location: Kington, Herefordshire, UK. Posts: 3,671	Re: Quad II test run. The chirrup on switch-off is a dead giveaway, too - something's squawking.

10th Apr 2020, 9:49 am	#167
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Yes I do have one working Quad II. Mike.

10th Apr 2020, 12:03 pm	#168
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Quad II test run. I would remove the valves from both, check they are both set to 15 ohms and on the same mains voltage selection, and wire both up with the link to the heater winding. You can then do a comparison of phase and amplitude at each turret between the good and bad chassis as we (you) did before. You could also include a more accurate measure of AC volts on each turret using your DMM. This way you can eliminate any issues that might occur from using different test equipment or procedure to GJ. Did you check the U/S marked EF86 base?

11th Apr 2020, 9:12 am	#169
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Hi PJL, The EF86 valve base I have checked briefly for low resistance but will look at it more closely today with a bit of luck. I will use my good Quad for comparing the various voltages and traces with the other one. I might just buy another OPT from Majestic anyway (if they still make them) , as if I found that I did not need it, I could always keep it for a spare for either amp, or even sell it on the auction site. Mike.

11th Apr 2020, 11:54 am	#170
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. I am checking out the valve bases and so far anode to earth is around 10 meg on both. Now I find that pin 2 on each valve connects to 2 on the Jones plug. This does not seem correct to the original quad circuit diagram ? On drawing, EF86 next to Jones plug does go direct, but the other connects with R8.?? Mike.

11th Apr 2020, 2:35 pm	#173
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. "That is an error in your wiring." I hasten to add, not exactly my wiring as the tag board and loom came to me in one piece which I assumed, (now wrongly)an original quad loom and board. Will compare all this part of the amp with the good Quad. Mike.

11th Apr 2020, 3:29 pm	#174
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Well the original, since early 64, to me, working Quad is wired in exactly the same way. So what is going on here, is the Quad drawing incorrect ? Keith Snook has re-drawn the original circuit and went to his site, but could not get in due to out of date certification of site. Mike.

11th Apr 2020, 3:49 pm	#175
sparkymike Octode Join Date: Dec 2006 Location: Colchester, Essex, UK. Posts: 1,076	Re: Quad II test run. Solved that small mystery. Pin 2 is a screen and as such does not show up on the Quad original drawing. Mike.