YMI's 12xxxx build - feedback please

[vanhalen5150]

Something you can try with the Hotplate is to reduce the attenuation and put a appropriate load resistor in the other speaker jack. This will decrease the compression but give you the same attenuation. All the attenuators I've tried at the lower volumes compress too much and tend to get a little buzzy sounding.

[YMI5150?]

thx, that clip wasnt worth posting...

i went back to my slave setup last night and ran Hardwire reverb (superb sunset reproduction) to the right side. i could have played all night. between the current state of the plexi and the model A with the resonance mod, it does the whole gammut. amazing tone. Now I need to focus on getting what I hear in the room recorded so you guys can hear an accurate representation for feedback. a whole other animal...

i am very close to getting another mic to record the verb'd right side rather than adding it via software. that pedal is remarkable. and so is the slave setup. now granted half of the drivers are v30s, which i know are not popular, the combonation with prerolas in the room sounds great!

BTW, those El Mencos are the $hit!

[vanhalen5150]

I have some of those Menco's lined up on the bay. Cant find the .0022 yet though.

[vanhalen5150]

Whats the voltage rating on that Menco .0022 you have?

[YMI5150?]

400 volts , .022uF

[vanhalen5150]

400 volts , .022uF

Oh, I thought you had a .0022uf in there as well.

[YMI5150?]

no, i just swapped a silver mica .0022 for a NTE poly cap. No huge difference but I'll leave it for now.

a couple frustrating things. one, i cant play a friggin minute without a mistake...two, i'm strugging to get what i hear in the room on tape. here's a phone clip from lunch. bite your tongue on the mistakes and try to hear the tone. this is slaved and obviously a very reasonable volume since the phone mic isnt clipping and you can hear the picking. Imagine if it was pushing some air! the resonance mod is in full effect here, cranked for the YRGM, and dialed way back for RD and others.
Remember this is a split of V30s and greenbacks. two cabs, the one on the right is wet, not that you can hear this in stereo.

i'm getting to be very satisfied. i think the next step is to increase the PI can to 100uf and tighten things up a bit. I can see the light, which is good. I can practice more and tweak less...

Cheers guys.

[vanhalen5150]

Thats really getting there. Lot of the correct frequencies there. The V30's are giving some extra none VH tones though. Almost dark like.

[YMI5150?]

update

last night i swapped the SM 500pf (mixer i think) and 47pf fizzy for lemco dogbones. played it a bit this afternoon and thought i lost some high end sizzle.

then i replaced the 68k AB CCs i had on the first stage for some Iskra 1W s that just arrived. the result is a fairly substaintial loss in gain and its muddier.

granted i'm evaluating this from what i hear in the room and half the speakers are V30s so this is all relative feedback, however, the loss in gain from CCs to Iskras should be a universal observation, as well as loss in sizzle when going from the silver mica caps to the lemco dogbones.

[Strat78]

To form the caps in a 67 or 68 build do the following (see pictures):
1)Pull all tubes.
2) Disconnect center tap from first mains cap and tape off the end so you don't get ellectricuted.
3) Disconnect the hot wire between the diodes and cap and insert a 2w 100k resistor. Note, that the wire from the HT fuse goes dirrectly to the first positive terminal of the cap. Connect aligator clips (from multi meter)on either side of 100k resistor, where I have the green dots.

Power up the amp fully and watch the voltage drop on the meter. It usually starts dropping from around 200 volts down to 50 volts in the first few hours. Depending on the condition of the caps, it might take two days for the voltage measured accross the 100k resistor to drop down to aprox 5 volts then you are done. The amp must stay on until the forming process is complete or you will haveto wate another fiver years before you can try forming those particular caps again.

Maybe some of you guys could varify this for me, vhjunkie, are you out there?

[vh junkie]

That is the basic methodology in forming the caps. A couple of caveats though:
1) Might not want to remove the preamp tubes, only because the preamp coupling caps might have their 400v rating exceeded. Check the voltage across these caps as you go. Be sure the volume controls are down!

2) If you are only forming an isolated cap (i.e. the PI cap), pull the power tubes, and use a 220k resistor between the (+)V wire and the cap.

Best to use a variac to slowly raise the voltages while monitor the voltage across the coupling caps, on the caps being formed, and any voltage dropping resistors.

[Strat78]

Yep, forgot about the variac. Will the pre amp filter cap form with the 12ax7's in? Here is a shot of how the alligator clips go.

[YMI5150?]

about ready. need to find an aligator clip for the other lead. initially thought I was measuring to ground. i get it now. thx
for the help. board's just about there. have larger diodes to thow on there as well as cooler looking bias cap. dont want to change too many things at once in case something doesnt work...

main board 2.19.12.JPG

(91.08 KiB) Downloaded 436 times

forming filters 2.19.12.JPG (87.58 KiB) Viewed 2817 times

[ValveStorm]

Better to just by the clips from RS that slip over the end of your existing meter leads. They have both alligator and the smaller ones too. Makes me a little nervous to see HIV leads hanging around.

[Strat78]

Wow, I kind of get a tingling feeling when Iskras show up on the board!
Where are we at now?