Bottlehead Forum

Bottlehead Kits => Reduction => Integration => Topic started by: oguinn on May 17, 2019, 11:19:31 AM

Title: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 17, 2019, 11:19:31 AM
I was listening to a couple records today and noticed a couple issues:

I'm planning to listen to a few more records, but I want to troubleshoot the amp's voltages and resistances first to make sure something isn't going to damage the amp. However, I'm not sure which manual measurements are valid after the upgrade was installed. For instance, the Integration manual lists only a few spots to check voltages - surely those voltages aren't an exhaustive list - and no resistances. But I also removed resistors and added new parts in, so I know there isn't a clean combination of the base Reduction and Integration manual checklists.

Does anyone have a quick hit list of which are valid, which aren't, and which are new areas to check?
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: Paul Birkeland on May 17, 2019, 01:09:45 PM
I would recommend just checking the voltages listed in the Integration manual.  The Integration increases the gain of the Reduction a bit, so while there may appear to be more surface noise, there's also more signal to go with it!  The low frequency issues that you're mentioning could be subsonic coupling between your speakers and the turntable. 
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 17, 2019, 02:30:29 PM
Oh, interesting, so that could be the cartridge picking up and re-amplifying low frequencies?
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: Paul Birkeland on May 17, 2019, 04:08:13 PM
Yes, there are tons of ways to deal with this that are all a bit dependent on your setup.  One of the worst case scenarios that I see is a pair of bookshelf speakers on a credenza with the turntable between them.  Though it looks stylish, it will not function stylishly. 
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 17, 2019, 05:07:43 PM
I did avoid that setup, although my woofer is on the floor next to the shelving unit the turntable is on. Not really sure where else I can stow that...
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: Paul Birkeland on May 18, 2019, 06:59:19 AM
In that case many would recommend a turntable wall shelf, provided that the wall it would be mounted to is well supported (most are).
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 18, 2019, 07:14:22 AM
That’s definitely on the list for the next place we live. I’ll play around with some of the rubber isolation pad material I have left over. Thanks, Paul.
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 18, 2019, 08:17:57 AM
Checked voltages.

2 - 63.6
18- 75.9
26 - 75.7
31 - 53.5

31 in particular looks pretty low. Any cause for concern?
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 18, 2019, 08:51:28 AM
Also rolled in a spare set of tubes. Those values were:

2 - 69
18 - 60.35
26 - 60.27
31 - 64.1

So a little lower on 18 and 26, then higher on 31. Are either set of numbers more desirable for some reason?
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: Paul Birkeland on May 18, 2019, 03:06:47 PM
Low just means strong emission, that's nothing to be too worried about.
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: oguinn on May 29, 2019, 12:08:25 PM
Paul,

I'm trying to understand why lower voltage means stronger emission. Let me know if I'm off base or misunderstanding.

Here's what I think I've figured out:

I'm doing my best to piece this stuff together with the limited knowledge I have pieced together from watching YouTube videos, so I'm sure I'm wildly incorrect in some or all places.
Title: Re: Which resistance and voltage checks do I use to troubleshoot after Integration?
Post by: Paul Birkeland on May 29, 2019, 03:09:53 PM
Is it the case that these are the plate resistors that go to ground?
With the integration installed, there are no plate loading resistors.

Since the 6922s are biased with LEDs, the bias voltage never changes significantly.  This is the mechanism that moves the plate voltages around so much.  In an old school circuit with cathode resistors and bypass capacitors, the cathode resistor will serve to stabilize the DC operating point in conjunction with the plate loading resistor. 

If you consider the case where the 6922 draws no current and is loaded by a resistor, the plate side of the resistor will be at B+.  If the 6922 draws all the current it can, the plate voltage would drop to nearly 0V DC (we would consider this a short).  Somewhere in the middle is the average expected value, with some tubes drawing a little less current and some drawing a little more current under these conditions.