Last edited by Tejaus ; , AM. I followed the switching circuit and the TR2 transistor assigns capacitor C24 paralleled with cathode resistor to produce a treble emphasis only on the clean channel. Unrelated to the silence of the clean channel contained in topic when many things are mixed without control is easy to get confused. Forget it. On the other possibilities I will give my opinion:.
Originally posted by Tejaus View Post. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat.
And if it goes wrong he can fix it himself. You can't do that with SMD. Capacitors are in contact with the grids and the bias voltage but I do not see any problem with them. SW3 selects K resistors in series with the signals virtual power reduction or close its ends by a bridge normal sound. SW4 makes a mute joining both out of phase signals. In this composition the complete circuit looks better:. Thank you Pedro. Then I guess this is something we can check if the "bias gets mysteriously dragged down and the problem is extremely difficult to locate".
I think if plate or screen shorts to grid were a common problem we would see much more bias circuit failures in all tube amps. I usually use 82pf on the crunch channel master and pf on the lead. At first glance it would seem necessary to increase the filter on the crunch but in this channel, with gain at 10 and the treble knob down to minimum something occurs: there is still a lively harmonic content at very high frequency.
Elevating the filter value excessively has a negative effect on the texture. In the lead however the effect by lowering the treble is different more natural and accept higher filter values. ECC83 Tungsram V2. The Bias PCB assembly is as follows: PR1: Bias mini-pot adjustment for pin1 which is one side of the push pull amp two output tubes in a watt amp and one output tube in a 50watt amp.
Pin1: Connected to the cathode of the output tube s which then goes through a 1 ohm resistor then to ground. Pin2: ground reference. Make sure amplifier is connected to a load with the proper impedance selected. StratoMarshall , Dec 25, Texasbluezman likes this. Thanks for posting that info StratoMarshall. I will see about labeling my printed out schematic with those cable assignments. I would think that Microsoft Paint might do that task? Just load your pdf into Microsoft Word and do it there!
Joined: Apr 3, Messages: Likes Received: Setneck , Dec 25, I was just looking at a few other circuits on the schem, trying to follow that CON cable info. Getting a headache already!
I was checking to see if the individual channel Presence controls are actually going into the phase inverter as in a traditional NFB style circuit. It looks as if that is correct and they are getting switched in and out. I had been wondering if it was set up like the Mesa Presence circuits on my Nomad, where it is just a cap bleeding high frequencies to Ground in the tone stack. But Marshall actually is using a switching traditional style Presence circuit. I am stumped though by two things.
Anyone know if this is actually on the amp, and if so, what is it? I have not traced it out yet. It is tied to the Crunch Presence circuit. But there is already another W4 on the schem, which is one of the output transformer primary legs. Maybe this is just a typo on the schem? I have never seen a huge cap like that in a NFB loop. I am wondering if that has something to do with the brightness, plastic sounding tone that has always annoyed me on the DSL and TSL?
A lower value cap would darken up the amp here, anyone tinkered on this one? I know a common mod is to put a. I am looking at the stock Dagnall output transformer taps. And here's some additional reference info if anyone is troubleshooting or needs it otherwise. By continuing to use Reverb, you agree to these updates, and to our cookie policy. Learn More. Listings Price Guide Reviews. Featured Listing. Buy Used. Reverb Bump. Quick Responder Quick Shipper. Add to Cart Make an Offer.
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