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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 10:06 am
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Retroverbial wrote:
I inherited one of those old Simpson 260's from my Dad......

Image

They're great multi-meters.

I also "liberated" a GI-issue TS-352/U VTVM before I retired which I use for heavy-duty bench work.

Arjay (fond of Roger Miller's line about "every lock that ain't locked when no one's around")

:mrgreen:


Well, they were going to "survey" it anyhow. Right?

michaelbpuccio,
Not sure if you can do this with other browsers. In firefox, I can right click on an image and then click "view image info". From that point, I copy the link.
When posting, I click the "Img" button above the area you type in, and "Paste" the copied link into that. Piece of cake.

(I guess it is "copy Shortcut" in IE)

Art


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 10:45 am
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Art1 wrote:
...didn't they have a more expensive model with a mirror built into the backing?....


You're right, IIRC it was the 260XL. Some guys in our shop got the XL and made a big deal about the better "accuracy", but I just kept the non-mirrored version and never missed the 1/10 ohm difference. :lol:

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 10:54 am
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shimmilou wrote:
...but I just kept the non-mirrored version and never missed the 1/10 ohm difference.


What's a little "Kentucky windage" among techs?

:mrgreen:

Arjay

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 11:04 am
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michaelbpuccio wrote:
...When I pulled the tube closest to the power tubes the crackle cut out dramatically, but had a real faint appearance. Installing and removing the next two seemed to have no effect as the noise was very noticeable...



From this, and your previous posts, you may need to replace the Plate resistors for the pi tube (R57 and R58). Might be a good idea to replace all of these same resistors for all preamp tubes while you are at it. When these resistors start to fail they can cause a static or crackle sound. One other thing that it might be is a bad tube socket connection, although the resistors are more likely. :idea:

When you plug your guitar into the "Power Amp In", this bypasses the whole preamp section of the amp, and can help determine if the noise is coming from the preamp or from the pi and output section. If noise is still present when plugged in this way, that indicates the pi and output section as the problem area. :idea:

To post pictures, you must upload them to a publicly accessible site such as PhotoBucket (free), and then copy the "IMG" code and paste in your post here. When you click "Preview" or "Submit" the pics will be visible.

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 11:39 am
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Shimmilou- i have replaced R4, R11, R16, R22, R57, R58 with replacement parts from mouser. I have yet to check with the guitar due to the fact that this is making the noise even when the volume is turned all the way down. I have re-flowed all solder joints on the three circuit boards.


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 12:01 pm
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OK, those are all of the Plate resistors. Yeah, try plugging into the Power Amp In and see what happens. That is what the others suggested, didn't think that you had tried it yet. :idea:

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 1:01 pm
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There are nice volmeter, I have a simpson 260 from 1970. But in real life as repair amp those voltmeter could give you false reading because their low impedance. I won't use anymore my Simpson for working in électronic stuff . I use my Fluke.

Simpson is only good for house AC volt checking or electric AC/DC motor


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 3:50 pm
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yeah, but back in the day (the 70's), the 260 and a good scope kept everything up and running. NavAids, planes, rockets, you name it.

Can't live without the digital now though.

Art


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 4:14 pm
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Don't forget the slide-rule. :lol:

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 4:16 pm
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shimmilou wrote:
Don't forget the slide-rule. :lol:


I had two. I don't know where either is now. :lol: And, yes, I did have a pocket protector (or two.)

Art


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 5:30 pm
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shimmilou wrote:
Don't forget the slide-rule. :lol:


Hey, slide-rules got us to the moon (allegedly).

:wink:

Arjay

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Sun Jul 31, 2011 11:48 pm
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[quote="shimmilou"][quote="michaelbpuccio"]
When you plug your guitar into the "Power Amp In", this bypasses the whole preamp section of the amp, and can help determine if the noise is coming from the preamp or from the pi and output section. If noise is still present when plugged in this way, that indicates the pi and output section as the problem area. :idea:

When I plugged into the "Power Amp In" it did exactly what you had stated.. But when plugged into either inputs or even not plugged in at all the crackle exsists. Where do I go now? . And also is there a way to bypass the pre-amp completely as i never use it at all anyway.. I play Rockabilly type music and use the clean side of the amp mainly, but i do use reverb and the tone knobs.


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Mon Aug 01, 2011 1:34 am
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Art1,
in '60 or '70 bench test meter was a tubes voltmeter , a VTVM, not a Simpson for the same raison I wrote ; too low impedance for the Simpson and all of these VOM
I have one of those VTVM, a Heatkit I built.

---------------------------------------------------------------------
Michael;

You still have crackle because you have trouble in the power supply ,bad solder or resistor maybe

1- Remove all your tubes , excepts the 2 power tube : Crackle= power tubes or power supply problem.

2-No crackle ; plug de PI tube, keep 6L6's plug ; crakle =problem in PI section

3- No crackle ; plug tube closest to PI tube; do same test until you find where crackle is coming


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Post subject: Re: Hot Rod Deville - Cracking
Posted: Mon Aug 01, 2011 6:12 am
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+1 stratele52, it could be a problem in the supply.


michaelbpuccio,

:lol: Re-read your last post; When you plug your guitar into the "Power Amp In", this bypasses the whole preamp section of the amp. This means that, V1 and V2, the tone controls and volume controls are all bypassed, leaving only the reverb, presence, V3 (pi), output tubes, OT and speaker, functioning for sound production.

Are you saying that you have no crackle with guitar plugged into Power Amp In? If no noise when connected this way, it's an indication that the preamp section is where the noise is coming from. This is what Retroverbial suggested to try in the first response to your post.

stratele52 may be right, power supply problem (connection, cap?). If not power supply problem, it may be one or both preamp tubes/sockets/connections that is causing the crackle. Have you tried retensioning the tube sockets for V1 and V2? (instructions link below) You may even have a bad socket, as you indicated that cleaning the sockets may have caused the noise to increase. BTW, what did you use to clean the sockets? You should use an evaporating cleaner, if not any leftover cleaner in the sockets could cause the increase in noise.
http://billmaudio.com/wp/?page_id=171

You would be well served to develop an actual troubleshooting procedure instead of the "sledge-hammer to swat a fly" approach that you have been using. When you randomly try this and try that, you may never learn what the problem is, and you can introduce other problems, further compounding your troubles. As has been suggested, use a methodical step-by-step approach and you will have much more success. Example, if you have no noise when plugged into the Power Amp In, you have just verified that the entire output section isn't causing the noise, so it would be a complete waste of time to disassemble the OT (which was a waste of time anyway). :idea:

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Post subject: Re: Hot Rod Deville - Cracking
Posted: Mon Aug 01, 2011 6:23 am
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+1 Shimmilou


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