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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 11:47 am
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upnorth2 wrote:
stratele52 wrote:
upnorth2 wrote:
If it's never been serviced I would start by replacing the caps/resistors on the filter cap board, screen and grid resistors on the 6V6's, cathode caps and resistors (if needed) to start with.

UN



Only if Parkside drive know how , if not he can do more damage than good job


I agree. If you're not comfortable/qualified take it to a trustworthy tech. Money well spent.

UN


Im good to work on the amps, I know how to safely discharge capacitors and double check stored DC with a meter.

My soldering isn't that great, so id like to get to the source of the problem before I mess with things that are likely not related.

To that end, probably a good idea to mention that this issue only happens when the amp is pushed to distortion. I think thats the most important bit of info to keep in mind when trouble shooting. When the amp is at volume 3 (for e.g.) no issues...


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 11:52 am
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ParksideDrive wrote:
Thanks Stratele

Did the amp always do that since you have it ? No, this a new problem,
Did you bought from second hand few days ago ? Ive had the amp for several years, didnt notice this before (but also, didn't crank it up that often)
Did you use single coil guitar or humbucker ? Humbucker Ephiphone Les Paul



You may have the answer ;

Humbucker +" but also, didn't crank it up that often = overdrive / distortion


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 12:00 pm
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[/quote]

You may have the answer ;

Humbucker +" but also, didn't crank it up that often = overdrive / distortion[/quote]

Right, I want it to distort. Listen to the 1st clip, the distortion is not natural, it pops and crackles etc.


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 12:21 pm
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ParksideDrive wrote:


Right, I want it to distort. Listen to the 1st clip, the distortion is not natural, it pops and crackles etc.



I did not listen yet :oops:


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 12:36 pm
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stratele52 wrote:
ParksideDrive wrote:


Right, I want it to distort. Listen to the 1st clip, the distortion is not natural, it pops and crackles etc.



I did not listen yet :oops:


Ha, no problem. With that information though, does that help pin point the issue.

We have:
68' Blackface Deluxe Reverb
Brand new tubes (purchased last week)
Sprague atoms in the doghouse

Issues: Clippy, crackly distortion when cranked (in addition to the amps natural distortion). Amp sounds fine when played at a low volume.


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 1:03 pm
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You should probably do some voltage comparisons as per the schematic if you're comfortable with that. It's hard to pinpoint without tracing with a scope or lifting and checking resistors, etc. The amp is worth a look by a tech.

UN


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 1:24 pm
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ParksideDrive wrote:
stratele52 wrote:
ParksideDrive wrote:


Right, I want it to distort. Listen to the 1st clip, the distortion is not natural, it pops and crackles etc.



I did not listen yet :oops:


Ha, no problem. With that information though, does that help pin point the issue.

We have:
68' Blackface Deluxe Reverb
Brand new tubes (purchased last week)
Sprague atoms in the doghouse

Issues: Clippy, crackly distortion when cranked (in addition to the amps natural distortion). Amp sounds fine when played at a low volume.


Look normal sound to me with humbucker


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 2:38 pm
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Stratele, the problem is most evident in the last 10 seconds of the clip 00:35-00:45

Its even worse than than normally, but the clip does illustrate the issue. Definitely something wrong there.

Upnorth. Ya I could take it to a tech, but it bugs me that I don't learn anything. I know how to be safe. Hands are never in a live amp, I use an alligator clip system to get my readings.

I have taking readings on all my vintage amps in the past, and I usually get lost quickly...They never match at all. Like 20-50 VDC higher than listed. Then the replies are usually

1) Are you using spec tubes including recto (yes)
2) How is it biases (to spec)
3) Probably just the higher voltage coming off the wall. Which kind of makes it tough to tell where to go from there. Especially when the readings match in one spot of the amp, but not another....

I appreciate your advice, and a tech is always my last resort. Im hoping someone who has had a similar issue will tell me which part of the circuitry specifically needs attention


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 2:46 pm
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Voltages are never same in the amp and if you look at schematic.
'60 power transformer are made to work on 115 AC volts , today we have 120 to 125

It is not a voltage issue IMO. I mean voltages reading will not help.
1-Check and replace if needed resistors on my last answer.
2-Reheat all power supply solder , not only the dog house. Power supply solder are everywhere.
Until it is not done ( 1-2 ) , amp will not work fine :(


Try on another speaker cab.
Try a single coil guitar.


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 5:04 pm
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Interesting update

So I decided I should do the easy stuff 1st. Sprayed all the tube sockets with Deoxit, worked them in and out.

Then I realized I hadn't checked channel 1. I usually don't have a tube in V1, as I dont use it and it gets me more grit on channel 2.

Put it in, amp works perfectly. Left it in, checked channel 2...also good to go.

Took it out, checked channel 2 again, problem is back...

So it seems like the lack of a tube in V1 (which as I understand, makes the 2nd gain stage work harder) Is whats causing this?

I bias the amp at about 70-80% of the tube specs rating. If I want to keep the tube out of the V1, should I be lowering the bias to compensate?

Thanks in advance guys, all this and still no soldering Iron, which is my preferred choice :)


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 5:25 pm
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stratele52 wrote:
Look normal sound to me with humbucker


I play both single cutaway and DC Pro through my SF Deluxe and I can't get that level of OD without cranking the beejeebers out of the amp and using a pedal.

One other thing to look at... the speaker. Could have damaged cone or have a toasted VC. You have an external cab you can run from the DR? I put a Weber alnico into my DR. A WORLD of difference in power handling and clarity of tone.

Image

Image


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 5:30 pm
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Hey BMW

Did you see my last update?

Oh yeah, she's cranked to 8...sounds awesome (when its not doing that think I'm sussing out)

The speaker seems OK, But I could easily try slaving to another cabinet. Like I said, it sounds 100% when below 5....also, it sounds great now with a tube in V1...


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 5:42 pm
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Okay, "when in doubt read instructions or in this case, post updates." :)

V1 is prolly needed, if anything, to keep proper B+ going to V2 anodes. Pulling V1 will raise the B+ going to V2 (less load). And input/gain stage tubes are sensitive to voltage. It's the biggest reason for strident sounding vintage amps on modern outlet voltages.

As for other interactions between V1 and V2, I kinda remember there is some kinda interplay. That the two stages are not 100% isolated from each other. Will need to study the old schematic.

Glad you got the thing fixed. Cheaply and easily. [insert :thumbup: emoji] :mrgreen:


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 5:51 pm
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Glad you got the thing fixed. Cheaply and easily Sort of...I'd still like to have V1 out, but without that nasty sound. Wondering if I should drop the Bias?


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Post subject: Re: 68 Deluxe Reverb distorts strongly when cranked
Posted: Mon Mar 26, 2018 7:40 pm
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Get a cheap 12AX7 and put it into V1. In this amp, the second half of V1 shares the cathode resistor and bypass cap with second half of V2. Pulling V1 will not only effect B+ onto V2 anode, but also the idle bias.

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