Fired it up, it works! Please check my voltages.

[Fischerman]

Fired up my ODS prototype just now. It worked almost perfectly first time...I got the NO/NC contacts on the PAB relay confused and connected to the wrong ones...easy fix.

Was hoping someone could check my voltages and see if they're OK...and maybe suggest a value change if needed. My amp is using a Fender 125C1A choke...the PT is a Hammond 272JX...OT is a Mercury Magnetics 50W Hiwatt. This amp has a Skyliner EQ, HRM, and BM PI values. The FX loop is in the amp but it's just idling rght now...I'm not playing through it yet. The FX loop node (B+6) is a 36K resistor off of the screen node...33uF filter. The dropping string for the PI/preamp goes 4.7K-18K-10K all with 22uF filters.

B+1 = 437
B+2 = 435
B+3 = 400
B+4 = 345
B+5 = 330
B+6 = 345

EL34
plates = 436
screens = 430
cathodes = 40mV
grids = -37 (it's maxxed...I need to change the range resistor)

PI
82k plate = 276
100k plate = 265
cathode = 42.5 (Rk = 470ohm)
bootstrap pt. = 41.1


FX loop / V3
Send plate = 345
Send cathode = 46
Send grid = 21
Return plate = 230
Return cathode = 1.7

V2
180k plate = 213
2.7k cathode = 1.9
120k plate = 219
1.8k cathode = 1.85

V1
220k plate = 204
3.3k cathode = 1.85
150k plate = 209
2.2k cathode = 1.75

The amp is very quiet (yessssssssssssss!...my biggest concern) and sounds pretty good for just plugging in an out-of-tune Strat and not having any knobs to tell where everything is set. I was a bit surprised at the OD channel...it's more like an extension of the clean channel (or at least can be) and has less gain than I expected. With both volumes on ~5, I can get the OD channel to play relatively clean and only distort when I dig in or play intervals. The Drive knob does have a nice sweep to it though...it gets pretty gainy at the highest end of the range. Does that sound right?

[dogears]

Looks pretty good.

I am surprised by your plate voltages on the PI, V1 and V2, considering the 437V B+. I bet a different brand will be 10V lower.....

Glad she sounds good! Did you play the OD with PAB on? They do get gainy!

[Funkalicousgroove]

Sounds good to me!! You may like it better with your v1& v2 voltages under 200, do you have an FET input or a resistor to ground?

[dogears]

LOL!! Great minds think alike. I assumed Matt had the 150K..... Although the PI plates are the Dlite values, so he may have a 220K!

[Fischerman]

Haha, you guys nailed it...I don't have the 150k 'FET simulator' resistor at all. I'll add it and if needed lower the 4.7k to 3.3k.

I have a 3 -position ON-OFF-ON panel switch that assigns the PAB to always ON, always OFF, or OD only. This amp just uses a standard 1-button footswitch to switch channels. I tried it both ways and also with the Mid-boost on. I just schlepped a speaker cabinet in the room and plopped it down...tons of stuff was rattling at any volume...hard to tell much about the tones. I'm gonna go install that resistor, measure voltages, and then break out the Paul and play for a while.

Thanks.

[tele_player]

When posting a list of voltages like that, it's very useful (essential, even) to also post the AC line voltage. It does vary, and has a big effect on your DC voltages.

[heisthl]

Most every clone I made has the V1 and V2 supply point (usually B+5) at under 310 volts. Your's may get there when you connect the 150K FET simulator.

[Fischerman]

Good catch tele player...I always put it on my schematics but forgot to list it here. It's ~122vac...typical for my home.

I installed a 220k and that got my V1 plates to 181 and 185 and V2's plates to 198 and 203...something very close to that. The PI plates were still at ~260 and ~270 (trimmer is on '0').

It definitely will sustain and breaks into feedback nicely...the attack is fairly crisp...not thuddy/fuzzy. Still learning how to dial this thing in...I have the HRM pots on the front panel. The HRM mid pot has such a huge effect.

Thanks for the help.

[Bob-I]

I installed a 220k and that got my V1 plates to 181 and 185 and V2's plates to 198 and 203...something very close to that. The PI plates were still at ~260 and ~270 (trimmer is on '0').

You might try a 330K then. You should shoot for 200 on V1.

It definitely will sustain and breaks into feedback nicely...the attack is fairly crisp...not thuddy/fuzzy. Still learning how to dial this thing in...I have the HRM pots on the front panel. The HRM mid pot has such a huge effect.

Thanks for the help.

Find the sweet spot on the HRM mid, usually about 50-55% total resistance. Set the bass and treble higher. Scott may jump in with exact readings here. As you see it's very sensitive which is why it's usually "set/forget".

[Fischerman]

Thanks Bob. I've played it a bit more and the clean is really nice but the OD is a bit thin/fizzy...that's with PAB on and mid-boost off. It's also a bit boxy. With both mid-boost and PAB on it's too mushy and with PAB off it's kinda wimpy. The attack is nice and crisp and it sustains well but there's not enough meat. And there is slight high-end fizz or 'sting' to hard notes. But for just first getting it up and running it's not too bad.

And I tried the FX Loop...it seems to work fine. I need to check it more because you can dail in some hum if you try...but using it 'nominally' it's fine. I need to find a happy medium between the two channel MVs and the Send Level control (both control the actual Send Level so it's a balancing act). I also upped the 36k dropping resistor to the FX Loop node to 47k...this made that node 330vdc (was 345vdc) and slightly increased the other voltages throughout.

[Normster]

The Drive knob does have a nice sweep to it though...it gets pretty gainy at the highest end of the range. Does that sound right?

Sounds right if you're using a 250K audio. I prefer a 250K linear for the drive pot on HRM.

[Fischerman]

Yep, 250K-A.

I figured I better take some pics before I mod it to hell and back and scorch every other wire with my iron.

I still have several mica caps to swap for ceramic disk (just got the package from Mouser)...and the white wire from the CS relay to the Send input cap is still the same wire I used to go straight into the PI input cap (when I was not using the loop) so it's sticking up...I'm still messing with this and didn't want to cut it just yet. These trannys were extras that I had lying around. A lot of the stuff on this amp is extra stuff I had lying around.
[img:800:600]http://i108.photobucket.com/albums/n4/m ... rside1.jpg[/img]
[img:800:600]http://i108.photobucket.com/albums/n4/m ... rside2.jpg[/img]
[img:800:600]http://i108.photobucket.com/albums/n4/m ... tshot1.jpg[/img]
[img:800:600]http://i108.photobucket.com/albums/n4/m ... tshot2.jpg[/img]
[img:800:600]http://i108.photobucket.com/albums/n4/m ... tshot3.jpg[/img]

[Bob-I]

I'm not sure, but I think that twisted bundle of wires by the relays may be trouble. I like to keep the relays closer to the tone controls, but I'd be more concerned about dress of that bundle.

[Bob-I]

I just noticed in the other thread that you used all shielded for the HRM. That could be your trouble. Too much shield can take the life out of an amp.

[ayan]

Yep, 250K-A.

I figured I better take some pics before I mod it to hell and back and scorch every other wire with my iron.

Can you tell me what the P/Ns for you ground and on/off & standby switches are? Did you get them from Mouser?

Thanks,

Gil