18Watt.com

hello everyone.
i'm pretty new here to the 18watt colony, but i am working on a 36 watter, and i feel i need a little bit of help that you guys might can offer.

so my 36 doesn't sound quite like what i imaginied it would. not just the general "bassiness" issue that everyone has. it's gainy, i mean...mad gainy, and not really all that loud. i know we all have our different opinions on what loud is...but i just imagined much more from this.

i took some voltage readings to compare to someone who has a 36er that's actually working right. here they are

v1:
1 - 141v
2 - *
3 - 1.14
4 - h
5 - h
6 - 141
7 - *
8 - 1.15
9 - h

v2:
1 - 135v
2 - *
3 - 1.01
4 - h
5 - h
6 - 219
7 - 135
8 - 135
9 - h

v3 (pi):
1 - 179v
2 - 72.4
3 - 98.2
4 - h
5 - h
6 - 175
7 - 63
8 -98.2
9 - h

v 4, 5, 6, 7 (all essentially the same):
1 - *
2 - *
3 - 9.8
4 - h
5 - h
6 - *
7 - 314
8 - *
9 - 307

v8 (rectifier)
4 & 6 - 296 AC

8 - 266 DC

B+ at can cap is 320v to OT and 308 to cathode (?) resistor

the PT has a 120 and 125v primary tap, which i'm using the 120, and the HV secondaries i have the option of 540v or 680v.
I was told to use the 540v taps, so that's what's going into it right now.

could someone please take a look and see if there's anything WAY out of whack. i listen to 36 watters on here all the time, and mine sounds NOTHING AT ALL like them. i mean, i guess somewhere in there the general tone is around, but not much.

HELP!! haha

thanks a lot

jake

p.s.
just so you guys know, i have compared this with the 36 watt voltage chart in the dowload section, and it is actually what prompted me to post.
it just seems that the high voltage stuff in mine is too low, prompting me to think i need to use the higher voltage taps, and the lower voltage stuff is too high, more specifically hitting the pi, which might explain how clipped and unmusical it sounds. i'm just trying to verify this.

Double and triple check all wiring and component values. Check all relevant solder joints and even the ones seemingly not so relevant. You should not have to go to the higher voltage taps. That will be asking for much more trouble in MHO. I could take voltage readings from mine 36'er, but it is based on the Weber 6M36TMB and I don't know how useful they would be. Good luck!

hey rick,
thanks for the reply...
just last night i pulled out my buss ground and tried a new star ground strategy. i'm pretty sure it was monster oscillation that was just draining the amp of any kind of fire. with the new grounding scheme, as well as changing to nice cliff jacks that are isolated...it really seems a whole lot better. the normal channel is nice and it's hum free. the tmb channel is noisy now, lots of radio station noise, but i think that's just cause i accidenly broke the ground tab off the mid pot, then tried to resolder it. i think it just doesn't have a good connection anymore.

that being said...my next step is to replace the pot and see if it fixes the interference. if so, then it's off to tone sculpting i'm getting pretty excited about that.

again, gracias

jake

Another good place to use shielded wire (besides the inputs to the grids) is from the middle treble pot connect to the phase inverter ( also the same place you can mod in a pre PI master volume). It can help tame down noise like that immensely. Also, if you're using a solid state recto and you have the 5V filaments tied into a socket with a SS rectifier in it, I believe that 5V AC supply can bring in some havoc. Let me know how it's going and good luck!

well, i rechecked the tab soldering, and it's solid. so i'm going to leave the pot for now just so i can get this noise under control. i just don't understand what might be causing it. i mean, is layout going to be the major contributor to the radio interference, or bad grounding, or both? haha hopefully one more than the other. and good call on the ss rectifier. i need to get some glass for it, but for now i'll just unhook the 5v heaters. i'll keep you posted. i think i might take a day or two off from it. my wife is getting a little frustrated with me the more frustrated it get. hahaha.
jake

Sorry about the mis-reference in the previous post. I should have said, are you using a shielded wire that goes from "D" on the master volume (Richie Hall's v.2.0) to "D" on the board (0.022 cap) which goes to pin 2 grid of V3? This may greatly help reduce interference. I use shielded wire on all my builds for the inputs and phase inverter as a matter of course. You may be able to get by without it, and some day you may play a gig a mile down the road from the local radio station, and then you'll think, "why didn't I shield that wiring?"

For the 5V filament wiring to the recto, I'm going to put a DPDT switch in the 5V line to the socket on top of the chassis, then you can just flip the switch when you switch rectifiers and the wiring shouldn't be a problem.

rick. problem solved. haha, i changed the tmb side to a ef86 channel. i'm really happy with it now. i have 5V4GA recto tubes. i was wanting to try one but i'm not sure if it will all jive. you have any knowledge on this?

The info I have on the 5V4 is this:

It drops the supply voltage a maximum of 25V.
It handles of load current of approx. 175 mA.
The filament current is 2 amp draw.
It can be used for amps up to 50 watts maximum power.

From this information, I think it would be pretty safe to try it in your 36'er. I'm using a 5AR4/GZ34 which supplies 225 mA and has a drop of of around 17V. It works great, of course this all depends on your dropping resistors,etc, but you should almost certainly be able to make the 5V4 work, I'd think. Good luck, and let us know how it works. Good to hear you got it straightened out! Rick