Valvestorm 18 watt TMB voltages

[ViperDoc]

Here are the voltages I measured on my board when firing up my Valvestorm TMB build for the first time yesterday. No spam intended on this build, I know I mentioned it in a few other threads. I'm using a Heyboer/Mojotone 18 watt PT/OT with JJ tubes. The sound is great and it's very quiet when not playing. It does have quite a bit of fizz when the gain is turned up that I wouldn't mind taming. Here are the voltages. Do these look right to you? I was a bit surprised (perhaps naively so) about the 20-30 mVDC readings on the grid stop(?) resistors of the EL84 tubes. That could be right, I'm just not sure. Thanks for looking at it.

vstorm tmb chassis W VOLTAGES.jpg

Valvestorm 18watt_TMB_Layout.pdf

[joeboo88]

I just googled "marshall 18watt voltage chart" and got a bunch of hits.
It even yielded Steve Luckey's awesome 18 watt PDF with voltages

[sluckey]

I would not worry about 20-30mV on the EL84 grids. Close enough to zero.

I also used the Mojo Heyboer PT. If comparing voltages to my voltage chart keep in mind that you have a TMB and I built the original Tremolo circuit so there will naturally be voltage differences due to the circuit differences, but the PI and PA voltages should be about the same.

I bet if you join 18watt.com you can find a voltage chart for your specific amp. I was a member back when your TMB version was being developed. Lot's of good info. But about that time there was a flood of posts about Epiphone Valve JR. So many posts that all other tech talk was drowned out. To deal with this, 18watt.com split into several different forums and only allowed 18Watt posts on the original forum. During the split a lot of member's log on info was lost. I never created a new account so I don't know what 18watt.com is like today. But back in 2006 before the split, there were a lot of friendly knowledgeable tech savvy members and a WHOLE LOT more clueless newbie types who only wanted to hotrod a Valve Jr. into the god of all noise amps.

[ViperDoc]

I would not worry about 20-30mV on the EL84 grids. Close enough to zero.

I also used the Mojo Heyboer PT. If comparing voltages to my voltage chart keep in mind that you have a TMB and I built the original Tremolo circuit so there will naturally be voltage differences due to the circuit differences, but the PI and PA voltages should be about the same.

I bet if you join 18watt.com you can find a voltage chart for your specific amp. I was a member back when your TMB version was being developed. Lot's of good info. But about that time there was a flood of posts about Epiphone Valve JR. So many posts that all other tech talk was drowned out. To deal with this, 18watt.com split into several different forums and only allowed 18Watt posts on the original forum. During the split a lot of member's log on info was lost. I never created a new account so I don't know what 18watt.com is like today. But back in 2006 before the split, there were a lot of friendly knowledgeable tech savvy members and a WHOLE LOT more clueless newbie types who only wanted to hotrod a Valve Jr. into the god of all noise amps.

Thanks a lot. I did post it there, I just wasn't sure how much activity to expect there.

[sluckey]

Thanks a lot. I did post it there, I just wasn't sure how much activity to expect there.

Maybe just use their search function (if they have one).

[Paul G.]

To help with the "fizz" add a 47pf cap between the plate resistors of the Phase Inverter. Add stability and cuts fizziness for sure.

[ViperDoc]

To help with the "fizz" add a 47pf cap between the plate resistors of the Phase Inverter. Add stability and cuts fizziness for sure.

I may have to do that. This amp has mega fizz.

[ViperDoc]

Some guys on 18watt have been helping me with this amp. It sounds great, but I'm still working on fizz reduction. I put a 47 pF cap between the PI plates and will install a "Paul Ruby" parallel zener/rectifer mod on the EL84 grid leak resistors. Anyone tried this?

http://www.paulamps.com/18watterbuzz.html

[ViperDoc]

When I measure the PT secondary output on this amp, I get 302-0-302 VAC. The PT SCH is rated at 290-0-290. I'm thinking of using a 10V 5W zener diode (or two 5V 5W zeners in series) to drop the voltage about 10 V. I can place the diode(s) either in between the EZ81 rectifier tube and the filter cap or after the filter cap on the B+ line. Does it matter?

I also noticed on another forum mention of heatsinking and insulating B+ zener diodes. What's the best way to heat sink a diode??? Do you just connect a floating (isolated) metal object to one side of the diode?

[ViperDoc]

I've had some buzz and fizz issues with this and the other TMB amp I built previously, the recent one being vastly improved. I noticed while tracking some guitar for a new record I'm doing with my band that the fizz becomes noticeable when mic'ing it. Go figure. The amp in the room is utterly dead silent when not playing. I put the chassis into a bluesbreaker open-back combo cab loaded with a Celestion G12M 65 Creamback and a Celestion Gold 10-inch speaker. The baffle is cut custom for that setup. I placed an SM57 off center on the Creamback and placed a Warm Audio WA87 mic in a phase-friendly location about 1-foot off the center, slightly pointed to the Gold side. You can notice the fizz right in the attack of each note. Is this normal for such a circuit? There's no EQ/compression post-processing except for some tasty reverb. I more-or-less leveled the mic outputs. This is not a honed performance by any stretch of the imagination, so pardon the obligatory talent disclaimer. This is the TMB channel. The MV is on 7 and the gain on 2.5. I'm playing a Nash custom trem-loaded 72 Deluxe with wide-range humbuckers.

18WattNoodle.mp3