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Post subject: 65 DRRI volume jump after around 30 minutes
Posted: Thu Jan 05, 2017 2:54 pm
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First off, let me state that three months ago I completed the Fromel Supreme mod but to the best of my memory this problem was occuring prior to the mod. I am okay with saying that it was my mod that caused the issue since I cant really remember. What I do remember is being dissappointed with the sound of the DRRI. Also, all tubes have been changed but I am absolutely sure the problem was pre tube swap. Also, for the record, this amp now sounds as good as any amp I have ever heard. Will share my tube selection if anyone is interested. Fromel Supreme Mod is on eBay.
THE PROBLEM: After about 30 minutes to an hour there is a significant volume jump. Happens on both channels so that's a start. Sometimes it will drop back down. sometimes go up and down a couple of times but then usually stays up. Really wierd. Thank you in advance for your thoughts. I always play through the tremolo channel though use only a "smidge" of reverb and never tremolo. Do not even plug in the switch.


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Thu Jan 05, 2017 9:28 pm
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You probably did the mod just fine. Your post reflects your attention to detail.
Your problem appears to be heat related. Its unlikely a part is failing. Over this span of problem history, a failing part would have expired by now.
More than likely, you have a connection problem. When you say really weird, I hear "lead-free solder" and all the weird problems caused by it.
Since the controls don't affect it, the problem probably is in the power stage or the bias supply.
In a case like this, I try not to overthink locating the problem and just resolder the entire amp. This is likely to fix the problem and prevent future soldering issues.
The lead-free solder is an industry-wide problem and techs have had to deal a lot with it. If you describe to your tech what to do, he will probably understand why.


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Thu Jan 05, 2017 10:33 pm
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Try a new matched pair of power tubes. Re-bias as necessary.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Fri Jan 06, 2017 3:49 pm
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mctabor wrote:
First off, let me state that three months ago I completed the Fromel Supreme mod but to the best of my memory this problem was occuring prior to the mod. I am okay with saying that it was my mod that caused the issue since I cant really remember. What I do remember is being dissappointed with the sound of the DRRI. Also, all tubes have been changed but I am absolutely sure the problem was pre tube swap. Also, for the record, this amp now sounds as good as any amp I have ever heard. Will share my tube selection if anyone is interested. Fromel Supreme Mod is on eBay.
THE PROBLEM: After about 30 minutes to an hour there is a significant volume jump. Happens on both channels so that's a start. Sometimes it will drop back down. sometimes go up and down a couple of times but then usually stays up. Really wierd. Thank you in advance for your thoughts. I always play through the tremolo channel though use only a "smidge" of reverb and never tremolo. Do not even plug in the switch.

I'll be interested to know your tube selection.

I bought my DRRI limited edition about 2 years and had some noisy tubes so I replaced them all. After trying various combinations I settled on:

V3 NOS JAN Philips 12AT7WA
V4 TAD RT011 7025 S
V5 Anything works here but currently using TAD RT001 12AX7A-C ECC83
V6 NOS Mullard CV4024
V9 Tungsol 5AR4

In V1 & V2 I like either TAD RT080 7025 WA or Tungsol 12AX7.

In V7 & V8 I like either TAD RT83 6V6GT-STR or Tungsol 6V6GT.

It sounds great!


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Sat Jan 07, 2017 7:05 pm
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You may want to take the amp to a good tech. It could be having issues with screen or grid stopper resistor(s) going out-of-spec. This may allow the amp to go into parasitic oscillations. Sometimes symptoms are sudden loudness or quiet.

Check the idle bias of the 6V6GT tubes, first.


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Mon Jan 09, 2017 8:40 am
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Thank you all for the tips. I think I will try the resolder first. Have to wait a few weeks as I have had hernia surgery.
I will post again if the resolder works. That makes since to me. I am also going to go over all of my previous work. When playing this past weekend the jump really annoyed me louder and brighter. it was after having the amp on standby for about 30 minutes between the end of practice and playing the first set.
Would using standy cause any issues?

As Far as the tubes that came with the amp and what I settled on is as follows;

Mike’s Fender DRRI tube layout from the factory
V1 GT-ECC83-S ACTUALLY IS JJ ECC83-S
V2 GT-ECC83-S “ JJ ECC83-S
V3 GT-12AT7 “ SHUGUANG 12AT7
V4 GT-ECC83-S “ JJ ECC83-S
V5 GT-12AX7-R “ SOVTEK 12AX7-WA
V6 GT-12AT7 “ SHUGUANG 12AT7
V7 GT-6V6-S “ JJ 6V6-S
V8 GT-6V6-S “ JJ 6V6-S
V9 Fender 5AR4 / GZ34 P/N 041400

Mike’s new tube layout
V1 = EH 12AX7
V2 = Ruby 12AX7AC7 HG+
V3 = NOS 12AT7
V4 = Ruby 12AX7AC7 HG
V5 = EH 12AX7
V6 = NOS 12AT7
V7 = NOS JAN Philips 6V6GT
V8 = NOS JAN Philips 6V6GT
V9 = Fender 5AR4 / GZ34 P/N 041400


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Post subject: Re: 65 DRRI volume jump after around 30 minutes
Posted: Mon Jan 09, 2017 9:12 am
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mctabor wrote:
Would using standy cause any issues?


Normally no, but if it does then the amp has a problem which needs to be identified and fixed.

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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