90's 2 channel DR: clean ch presence affecting dirty channel

[professoro]

Hey all,

Just looking for some help for a buddy of mine.

He has a dual rec that has a problem where the presence on the clean channel affects the presence on the dirty channel. It happens across all settings i.e. diode/triode/modern etc.

http://www.youtube.com/watch?v=QBewr7sr07Q

If anyone's got any advice or understands why it's happening your help is appreciated.

 

[fluff191]

Does the presence on the dirty channel do anything? Is it like BOTH controls are affecting the dirty channel? And what happens if he clones the dirty to the vintage setting?

 

[professoro]

From what I understand both presence channels are still in effect -> dirty channel becomes very shrill.
It happens regardless of being cloned or not. It's such an odd issue.

 

[94Tremoverb]

It sounds like it's stuck in Red to Vintage Clone mode - that does normally happen in that mode, but if he's sure he has the switch set to Normal, it may be a fault in the switching matrix or a bad LDR.

 

[UnderJollyRoger]

I don't know the layout, but it sounds like a bad relais or something like that. I would guess that when changing channels, the presence controls are switched, but with a bad relais, maybe both stay on in one channel, acting parallel or serial. Depending on the circuit, that gives the Presence Range a huge boost ...

(there's a chance of repairing relais if you switch often enough, sometimes they start working again)

But other people here probably know it better

 

[94Tremoverb]

The 2-channel doesn't use relays except for the master channel control and the FX circuit bypass, so it can't be that or there would be far more problems. All the rest is done with LDRs, like on the Tremoverb. I had a look at the schematics and I can't see any LDR failure that would leave the NFB loop - which is what feeds the presence control on the Orange channel - stuck *on* (as opposed to off) for Red to Vintage, so it may be the cloning switch itself that's stuck.

If it is an LDR failure it's LDR19, which is the NFB loop switch, but I've never come across an LDR fail short-circuit, ever - they always fail open as far as I know. (Although I could be wrong.)

 

[MesaENGR412]

I want to see the REST of that KL Explorer he's playing :shock: Hope he figures out hte problems. Sweet looking Dual Rec too.

-AJH

 

[professoro]

Thanks for all the feedback guys.
I haven't heard back from my mate in a while so i'm hoping he's had some luck with his tech.
If anyone has anymore info though it's still appreciated!

 

[volkair]

Hey ...
I' ve got the same problem with my Dual Rectifier, but I thougt it should be like that, because I remember that I've heard about Presence-controls affecting each other.
So I recognized that my Channel- Status-lights use to have a problem. Sometimes they won't work. When I flip my finger slightly towards them, then the light returns. Yesterday both lights were on, but darker than normal. After doing the same procedure, the activated channel-light returns and the other went off.
Somebody get us a doctor..

 

[cradlefish]

After reading this post I went to test it out on my Recto as well. Behold I have the same issue, it's not too bad and the difference isn't too drastic but at the same time I can back my presence knob for my distorted channel to balance it out. I think it may be a normal thing for the 2 channel rectos.

 

[94Tremoverb]

I' ve got the same problem with my Dual Rectifier, but I thougt it should be like that, because I remember that I've heard about Presence-controls affecting each other.
So I recognized that my Channel- Status-lights use to have a problem. Sometimes they won't work. When I flip my finger slightly towards them, then the light returns. Yesterday both lights were on, but darker than normal. After doing the same procedure, the activated channel-light returns and the other went off.

The channel status lights can do that. The problem is a loose connection between the LED itself and the holder where the wires go to - the FX loop light does it on mine. One day I will remember to bother to do something about it! But since I never turn the loop off normally, it doesn't really matter...

After reading this post I went to test it out on my Recto as well. Behold I have the same issue, it's not too bad and the difference isn't too drastic but at the same time I can back my presence knob for my distorted channel to balance it out. I think it may be a normal thing for the 2 channel rectos.

It's only normal when the Red channel is cloned to Vintage (this is mentioned in the manual), but is definitely *not* supposed to happen when it's set to Modern. If it does, there's something up with the switching.

I just checked it on my Tremoverb (which is identical in terms of this feature) and it's working correctly as per the manual.

 

[professoro]

Hmm...the problem with 15 year+ amplifiers.
I haven't heard from my mate in a while so who knows how he's going.