UP dumble for sale

[Smokebreak]

Very nice layout Jelle! This confirms what I saw in the pics and how I wired my amp. Of course my VR has no mid pot for the normal, and I stuck the BM side mid on the back. My only differences are in the BM stack/vibrato channel side. I used a 1M for bass, 25K for mid, and a 500P treble cap. Is the 250K bass and 250p treble cap verified? I guess i was going off more the HRM stack as an assumption.
As far as the Hog vs UP, piecing information together...

"Classic stack (low plate) on one channel, Blues master (high plate) on the other"

...with associated PABs on each channel.

I gigged with this amp the other night on a roadhouse/honky tonk gig and the amp was great! This amp as a ton of low end(which is why I can see a smaller bass pot ), but it can be moderated and it's not real muddy. That in itself made the VR thump in a way it never has with that lil OT. I played the vibrato side solely, and I kept the bright cap on all night, with the vol at 3, and the MV backed off just a hair. Still pretty clean, but much richer than stock.
The boost(47K/22M on the relay) is ridiculous IMO. The volume jump is massive, unuseable as a "boost". I just use a pedal anyhow, but made mine 47K and stock 220K for the switch, via the 1979 VR push pull pot on the Volume. Still too much. What's interesting here is that 47K really helps chill the amp out too, and moderates some bass, especially with all the other mods that jack things up.
I'll go high plates on the Vib side next and see what happens.

[jelle]

Maybe that 47K is a 470K instead, I don't know. I went off the same pics as everyone else.

[Smokebreak]

I think 47K is correct for the "stock", non-boost function. That's what I saw too. Besides, there's not a big difference between 470K and 2M2, as it's parallel with the reverb's 470K. Definitely a tweakable to taste area though

[sonicmojo]

I guess I should have read the later posts in this thread more carefully. I just finished my '74 Vibrosonic Reverb HH and the funny thing is that I landed exactly at 220k to ground on my boost also! I may play around with raising the 47K up a bit and maybe go higher that way but 22M way too much for my taste. In fact I didn't see much difference until I started getting down under 1M. I thought the 2M2-.1uf on V3 robbed too much reverb so I took it back out.

[sonicmojo]

Ah, now I see why the reverb was tamed after cranking this a bit more today.....reverb over 3 without that V3 change gets crazy when cranked. Can just turn down the knob to avoid. My amp has that honking sound for sure, especially with my 15" JBL. Fun stuff.

[jelle]

Awesome! Glad the drawing helped.

jelle

www.welagen.com

[sonicmojo]

The drawing is awesome and inspired me to do some experimenting! I think I like this enough to full on install a relay and footswitch for the boost. I'm now dissecting how the "sum of the parts" affects the sound. I gather the slope resistor of 33K starts the chain of events to be heavier and thicker and all the other "Marshally" cap values add to it. I'm still trying to figure the value of the resistor/cap on v3 as the colors to me look something different than 2.2M but I'm thinking you were going with that based on what is in an SSS perhaps? I'll tweak more in that area to get an optimal reverb mix that I like. My amp also had a bit less high end on the vibrato channel when it was stock and with this mod that is really accentuated where my treble control stays near 10 so I'll be trying a few things there too.

I noticed an non-shared cathode cap/resistor on V1 pin 8 in pics that is not in the drawing. Looks like a typical 1.5k.

[Smokebreak]

Very cool! IIRC the cathodes were split on V1b and V2b. I assume the only reason you would want to do that is if you wanted to change the values
I was actually surprised I couldn't see any 5uf caps here. The splitting certainly would point one in that direction though...sure is a lot of bass in the amp..
It certainly looks like the LFB on the driver tube is 3M3, but honestly, I don't think 2M2 vs 3M3 is really gonna matter in this spot.

Of all things, I've spent the last hour troubleshooting the reverb on my VR . Time for a new tank.

[jelle]

I noticed an non-shared cathode cap/resistor on V1 pin 8 in pics that is not in the drawing. Looks like a typical 1.5k.

Glad you guys are having fun with it.

The V1A section has a cathode of 1.5K and 25uf grounded to chassis, V1B on the board, same 1.5K//25uf. That drawing is not perfect... But I tried.

The Reverb driver LNFB could be 3.3M. The actual value required seems to vary per amp.

[dorrisant]

The 22M on the boost... notice the green/blue color band... it would make it 2M2 or 22M. It looks like the same color as the 10M, right? So 22M then?

I see orange on that LNFB on V3 as well.

Is that a 22k on the bias pot?

Looks like the location for V5-3 resistor/bypass cap is on the socket, not V4-3 as in the drawing, (no offense Jelle). Also looks like V4-3 used the res/cap location intended for V5-3 so that V5-3 values could be changed. Should we assume that V4-3 values are 2k7/25µ? If it is located where I'm referring to then I think the cap value is changed... doesn't look the same size or color as the stock Mallory next to it. The resistor is kinda covered by the trem caps. In the low res pic I have that is taken of the input end I see red and green showing through... maybe not.

Does anyone have clear pics of this other than the one Smoke posted toward the bottom of page 3? I have been trying to work off of some lower res pics. PM or email

[jelle]

If I have free moment I will fix the errors, thanks for being a second eye, that is always helpful.

[dorrisant]

If I have free moment I will fix the errors, thanks for being a second eye, that is always helpful.

No worries... thanks again for posting what you did!!

[Smokebreak]

Hey Tony, is this one better than the one you have for the input? I got it from the same place I got the other one, which is better resolution....the gear page

I see brown green red on the V4-3 recovery stage cathode.

[dorrisant]

Those are the same resolution as what I have... but thanks anyway.

[dorrisant]

Does anyone know if the filter cap values are different? I would think so.

I see orange and green on the feedback resistor at V3 too. 3M3