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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sat Jul 21, 2012 7:48 pm
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Hou-Tex wrote:
bluesky636 wrote:
Hou-Tex wrote:
Maybe my DVM need to be calibrated.

Thanks anyway man.


I doubt it. I have never seen a DVM that far off unless it had been damaged. There really is no user calibration on a DVM like on the old vacuum tube voltmeters. I think you need to figure this out before you do some damage. Even Stinger 22's plate voltage is a little high but at least closer to the schematic. Yours is off the grid in my opinion.


Metrology is part of my job and yes, DVM's can be calibrated.

No disrespect, and thanks for your help, but I was just looking for a simple formula.

BTW, tyronnes tubes ran the same as mine.

viewtopic.php?f=13&t=58087


Well, I did find a typo in my original caculation so I apologize. Your readings are right at 70%. However, I still do not understand how you can be reading a plate voltage of 430 VDC compared to a schematic value of 396 VDC. Something is wrong somewhere. But if you don't care about figureing out what is going on, then I guess I don't care anymore either. I was just trying to help you prevent damage to your amp. I'm unsubscribing from this thread now since there is no reason for me to continue.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 1:38 pm
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OK so the tube is 14Watts and voltage is reading 409 so (14/409)*.7*1000 = 23.96

So 24mv and I'm at 24.65 average.

So going a little hotter will add some early breakup but shorter tube life? What about tone?
Going lower will give more headroom, and longer tube life. And what about tone?

Also my multi-meter has hard wired probes. So the best I can do right now is try to tape the probes ends together with electrical tape. So that may be affecting my readings.

Any tips on where to get a reasonably price meter that use the fatter connecting pins on the bias meter? Radio Shack or Home Depot? Online. What do you call that type plug.


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 1:45 pm
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Stinger22 wrote:
Going lower will give more headroom, and longer tube life. And what about tone?


"Brittle", "sterile", and "mechanical" are some of the adjectives typically used to describe the tone of an amp that's biased too cold.

Arjay

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 2:50 pm
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Stinger22 wrote:
OK so the tube is 14Watts and voltage is reading 409 so (14/409)*.7*1000 = 23.96

So 24mv and I'm at 24.65 average.

So going a little hotter will add some early breakup but shorter tube life? What about tone?
Going lower will give more headroom, and longer tube life. And what about tone?

Also my multi-meter has hard wired probes. So the best I can do right now is try to tape the probes ends together with electrical tape. So that may be affecting my readings.

Any tips on where to get a reasonably price meter that use the fatter connecting pins on the bias meter? Radio Shack or Home Depot? Online. What do you call that type plug.


Don't do the Radio Shack DVM, I read a lot of negative reviews on them. And they are called "Banana Plugs".

Although Im new to all this, I find the more questions I ask, the less response I get. I think the experts are trying to make us figure this out on our own. Maybe it's in order to educate ourselves. It would be nice to get a short answer so we can quit tweaking, and get to picking.

Especially since we could be "Damaging" our amps.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 3:43 pm
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OK picked up a good one and readings are 413 on the plate voltage so at the 14 watts that means 23.7 for 70%. I bumped the lower reading tube to 23.7 and the other reads 26.6 now. These were purchased as a matched 6V6GT Tung-Sol set.


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 4:14 pm
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Hou-Tex wrote:
Although Im new to all this, I find the more questions I ask, the less response I get. I think the experts are trying to make us figure this out on our own. Maybe it's in order to educate ourselves. It would be nice to get a short answer so we can quit tweaking, and get to picking.

Especially since we could be "Damaging" our amps.


Going back through this thread, it appears to me that every question you have asked has been answered in great detail. In fact, it has taken 8 pages to explain a process that most people grasp in 8 posts.

You want a short, simple answer? Here it is:

Select a bias setting that results in anywhere from 50% to 70% of maximum plate dissipation and sounds good to you and call it a day.

And yeah, us "experts" like to make sure that we are not giving anyone advice that may result in damage to their amp. We're kinda funny that way.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 9:09 pm
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Stinger22 wrote:
OK picked up a good one and readings are 413 on the plate voltage so at the 14 watts that means 23.7 for 70%. I bumped the lower reading tube to 23.7 and the other reads 26.6 now. These were purchased as a matched 6V6GT Tung-Sol set.


What formula did you use in order to calculate plate dissipation?

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 9:29 pm
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(Max Plate wattage rating times desired idle wattage percentage)/Plate volts = Plate current.

For 70% idle dissipation:
(14 x .7)/413 = .0237 (23.7 mA).

For 50% idle dissipation:
(14 x .5)/413 = .0169 (16.9 mA).

Cathode current for a 6V6 will be about .002 (2 mA) higher than Plate current, so Cathode current is usually close enough.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sun Jul 22, 2012 10:06 pm
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shimmilou wrote:
(Max Plate wattage rating times desired idle wattage percentage)/Plate volts = Plate current.

For 70% idle dissipation:
(14 x .7)/413 = .0237 (23.7 mA).

For 50% idle dissipation:
(14 x .5)/413 = .0169 (16.9 mA).

Cathode current for a 6V6 will be about .002 (2 mA) higher than Plate current, so Cathode current is usually close enough.



Thank you very much.

So I'm sitting at

14x.7/430x1000=22.79.

Thanks man.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Mon Jul 23, 2012 5:34 am
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For 70% idle dissipation:
(14 x .7)/413 = .0237 (23.7 mA).

Or (14/413)*.7*1000= 23.7mA as per the instructions that came with my bias probe.

I let it sit with power on for about 40 minutes went back and checked and was getting 409V again and 23.2 and 25.9 bumped up to 24 and 26.3.

Still concerned about the spread between the tubes.

BTW I have bias'd amps, SCXD BDRI, for years just using my multimeter setting them at exactly the mfg/tube spec. This is the first time I have had an actual probe that measures the plate current also to really fine tune it to personal preference. So while not an expert certainly not an amateur and like many on the forum just enjoy discussing these things and even posting simple questions to further those discussions for all. So 8 pages of discussion with everyone, complete novice to expert, is fine with me.


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Mon Jul 23, 2012 7:36 am
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Stinger22 wrote:
...Still concerned about the spread between the tubes...


Swap the output tubes positions and see if the higher current remains with the tube, or remains with the position. If the former, the tubes are not matched as advertised and I would send them back for exchange. It happens, and a reputable dealer will exchange them. I see it more often with "matched" quads that will occasionally have one that is not matched. Unless you buy GT or MB tubes, the tubes are likely not matched under actual amp conditions and you will sometimes get one that isn't matched when installed in the amp.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Mon Jul 23, 2012 9:10 am
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Will try the swapping them. Also went through my tube box and have a set of EH 6V6EH, which were the original tubes, and also a set of JJ 6V6S matched, both have 27 on the box. May try the JJ's this time.


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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Mon Jul 23, 2012 10:42 am
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IMO, the EH would be the better choice to get a more traditional 6V6 sound and the JJs sound more like a 6L6 by comparison. But, try them both and see which you like better.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Mon Jul 23, 2012 1:16 pm
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Stinger22 wrote:
So 8 pages of discussion with everyone, complete novice to expert, is fine with me.


Exactly!

We all learn and share information, and if you look, there are a lot of "Guests" that could be potential new members here.

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Post subject: Re: Vintage Reissue '65 Deluxe Reverb mods?
Posted: Sat Sep 22, 2012 8:11 am
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Hard to believe it's only been 3 months. This is my update. I have messed around with different tubes, changed my speaker out to a Cannabis Rex, added an external speaker cab using the stock speaker, channel jumping with a Radial Bigshot A-B-Y box, so this is todays report.

A have been collecting glass and a few given to me recently. But first I decided to check the Bias on my power tubes since I haven't done it in about a month. Tubes are JJ 6V6's.

V7 was 21.1 @ 422 vdc.
V8 was 20.3 @ 422 vdc.

That's pretty cool so I decided to roll the dice and go a tad hot. Why not? I got extra tubes! 8)

I'm now at

V7 25.1 @ 418 vdc and V8 is now 24.3 @ 418 vdc.

Here is my other tube arrangements.

V1, V2 and V3. Jan Phillips NOS 5751's.
V4 and V5. Raytheon JRP 12AX7's.
V6 is stock.

I have noticed gradual improvements along this 3 month journey, and sometimes I wasn't happy with the results, but today I am totally blown away. I now have a reverb that sounds worth a damn! :lol:

Anybody want to buy some effects pedals? :P

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