T Attenuator Termination Kluge

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JR.
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Re: T Attenuator Termination Kluge

Post by JR. » Sun Jul 28, 2019 4:27 pm

If the pot element wipers are on a splined shaft, it could be something simple like shaft being off one tooth. That might explain all being off the same resistance.
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I recall a friend's studio when some clumsy customer spilled a glass of orange juice into his P&G faders... no problemo some isopropyl alcohol(?) and blow dry then they were good to go.

JR

PS: Yes back in the 80s I recall finding all kinds of stuff, lots of roaches (not the insect) inside Loft delay line/flangers returned for repair. We always built "producers desks" into the loft consoles so the studio pukes had a place to stash their drugs. :lol:
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Gold
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Re: T Attenuator Termination Kluge

Post by Gold » Mon Jul 29, 2019 2:15 pm

I popped the back on this and took a look. I think I see what's going on. The shaft is smooth without splines. The wiper is two small fingers. The wiper is attached to a brass disc which sits above the stationary resistive track. The brass disc is held in place by a set screw that pushes against the shaft.

The wiper doesn't extend all the way to the pin at the clockwise top of the throw (what would normally be the input pin). I think I need to loosen the set screw and rotate the brass disc until it touches the track that extends to the input pin. I have a feeling if this works I'll have to start with the deck closet to the top and work my way back.

All the decks on this switch are not measuring the same. I have a feeling whoever assembled this was having a bad day.

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mediatechnology
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Re: T Attenuator Termination Kluge

Post by mediatechnology » Mon Jul 29, 2019 2:47 pm

Sounds highly repairable.
I think you're right - that one may have gone into final test after a long pub lunch.

Check the tracking after you adjust the end stop.
What they may have done was adjust all the sections at some intermediate value to optimize tracking.
If the track of the pot is within their manufacturing spec, than an optimization of mistracking should still cause the wiper brush to land on the "hop off."
Eyeballing it though may get it within tracking spec.

A quick and easy way to check tracking between two sections is to ground and drive both ends like they normally would be used and then read with a floating voltmeter the difference potential between the two wipers.
It forms a Wheatstone bridge with the bridge error the tracking error.
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Gold
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Re: T Attenuator Termination Kluge

Post by Gold » Mon Jul 29, 2019 2:55 pm

I'm not sure I want to become an RF-15 expert. I can see a day or two disappearing trying to fix these. I have a quote coming for TKD's. If the TKD price isn't too bad I'll just bite the bullet. I can use these elsewhere if they require a bunch of attention. Finding the sweet spot by experimentation between channel matching and total resistance for four decks twice doesn't sound easy or enjoyable.

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Re: T Attenuator Termination Kluge

Post by Gold » Mon Jul 29, 2019 3:32 pm

I played with it a little and I'm not hopeful. The smallest amount of resistance I can get on this deck, at the top of the throw, by rotating the brass disc with the wipers, is about 37Ω. This is the most accessible rear deck. If I can't even get the first deck I try to behave I'm not hopeful about the rest.

Maybe they just gave me the shit they had left over before they discontinued this model.

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JR.
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Re: T Attenuator Termination Kluge

Post by JR. » Mon Jul 29, 2019 3:56 pm

I agree with Wayne, sounds fixable... (set screw).

Maybe somebody who lives near you is willing to tinker.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Gold
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Re: T Attenuator Termination Kluge

Post by Gold » Mon Jul 29, 2019 4:08 pm

I'm not throwing good money after bad. Once it's dis assembled it's easy to see the construction method. I clamped the shaft so it wouldn't move and very gently rotated the disc after loosening the set screw. 37Ω was the smallest value I got on that deck before it went open circuit. So far the smallest value I've measured on any deck is 25Ω. 25Ω is on the other unit. Every value on this unit is higher than that.

Radardoug
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Re: T Attenuator Termination Kluge

Post by Radardoug » Mon Jul 29, 2019 4:30 pm

Maybe this deck is a different value from all the others? Talk to P&G?

Gold
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Re: T Attenuator Termination Kluge

Post by Gold » Mon Jul 29, 2019 4:47 pm

Radardoug wrote:
Mon Jul 29, 2019 4:30 pm
Maybe this deck is a different value from all the others? Talk to P&G?

I don't think so. The smallest value I get on any of the decks at the top of the throw is 25Ω. On the deck I played with the smallest value I could get was 37Ω and that was very touchy. I can't consistently get that value. It's more like 44Ω. All the other decks are different values.

I just wrote a P&G distributor. There was no service contact on the main website.

Gold
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Re: T Attenuator Termination Kluge

Post by Gold » Thu Aug 01, 2019 3:24 pm

Dale Manquen's son Luke took over MANCO. I have a correspondence going but I'm getting less optimistic by the day. He didn't seem like he knew the answer of the top of his head. The spec sheet makes no reference to minimum series resistance.

I'm still trying to get a quote for the TKD rotary faders. I would like a detent at the fully CW position to aid in level calibration. TKD only offers a center detent version. Hopefully they can do a custom version with the detent at the top of the throw. Otherwise I'll just get regular ones with no detent.

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