troubleshooting 5F1 no sound

Well I hoped I didn't need to post to ask for help as I wanted to find it myself, but I'm hoping to be able to use this new build for the first time tomorrow as we have a gig to play and I'd love to have it with me..

Anyways, I decided to install a switch for the multi tap mojotne OT and I think it's wired right along with the input jacks, but if you could have a look and let me know if you see anything that could be wrong, I'd appreciate knowing.. I realized I hadn't installed the wire from the 22K resistor to the output jack and hoped that would solve it, but no cigar....Thanks in advance..

first E-Cap 327VDC Is that a bit low..I have a borrowed PT in there right now and wondered if that might be lower than it should...read that they should be closer to 350-360

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found the cathode biasing resistor tubedepot sent me was 0 Ohm 5watt and all i had was a 330ohm 5 watt in the parts box and after installing it boy did the voltages jump B+ went from 327-372...2nd e-cap went from 206vdc to 309......3rd went from 180- 270 v1 pin 1 went from 115 to 180VDc... not sure if I could cook anything at that high of voltages but I will order up the proper 470 ohm on tuesday and replace it, but I still have no sound.. :)

Did you make the connection under the board... last power supply node to the junction of the two 100k plate resistors? Every other connection is visible.

330v will work just fine.

OT wiring near the preamp tube isn't a good idea.

Did you make the connection under the board... last power supply node to the junction of the two 100k plate resistors? Every other connection is visible.

330v will work just fine.

OT wiring near the preamp tube isn't a good idea.

Yes, all continuity checks out for underboard wire routing

when you say 330V will work fine, that was with the 0ohm cathode resistor in it....are you suggesting leaving it in there or should I get the 470 as perscribed because with the 330 OHM in it now it put it up to 372VDC

have the OT wiring near the preamp tune will cause noise or hum?? Where should it be relocated to ?? Thank you

does the input jack wiring look right to you guys??..

FWIW,
when I test the output jack there is continuity to grd on both lugs

I rerouted star grounds and disconnected 4 ohm tap and ran direct in hopes that might change things for the better aaaand it didn't ..:sad:

http://i271.photobucket.com/albums/jj134/livtohunt60/19reroutedgrounds.jpg
http://i271.photobucket.com/albums/jj134/livtohunt60/21reroutedstargroundstone.jpg
http://i271.photobucket.com/albums/jj134/livtohunt60/20reroutedspeakerwires.jpg

What is a 0 ohm resistor?

When you say 330V will work fine, that was with the 0ohm cathode resistor in it....

Tried that once. It works for a while. Then little lightning bolts start shooting around inside the 6V6. No kidding!

Not generally a good idea in a Champ.

have the OT wiring near the preamp tune will cause noise or hum?? Where should it be relocated to ?? Thank you

It might crosstalk.

Just keep it away from the preamp. You might get away with it in a Champ. If you end up building a high gain amp it's more likely to cause problems.

What is a 0 ohm resistor?

That's the ol' copper comp resistor aka straight piece o' wire. :lol:


Is it up and running yet? I finished another one a couple hours ago. I was workin' on my mad scientist demented laugh. My top secret combination of high grade surplus resulted in the most sinister distortion tone this side of some hideous pedal. No pedals involved of course. Straight into the amp. Big bass, chimey top and all dripping with harmonics that made me overindulge in pick squeals and pinch harmonics.

It's a top secret combination because two of the ingredients are relatively unobtainable.


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What is a 0 ohm resistor?


tests 0 too
http://i271.photobucket.com/albums/jj134/livtohunt60/30.jpg

Noooooo, it's not running yet.....

I think the boys at tubedepot thought it might be fun to send that resistor to me when I ordered the 470...ya those lighning bolts would be great in a dark room...just in someone elses amp..:)

I'm praticing my sinister laught impression and I'd be more than happy with a low secret solution MuchXS at the moment but hey once I get this supposed prized unit up and breathing tone Maybe then :) you'd care to share the recipe of this top secret tone monster you speak so highly of...

I'm suppose to be going to an outdoor party tonight with some top notch local players in attendance and I'm so wrapped up wanting to get this amp running I could care less if I attend, which is not like me to miss a good bash..this amp addiction has got a firm hold I'd say..

does the input jack wiring look right to you guys??..

Input jacks are a little different from the way I do 'em but they look functionally correct.

when I test the output jack there is continuity to grd on both lugs

Which is normal. You're measuring through the OT secondary back to ground. The secondary is just a whole buncha wire that leads back to ground.

I'd be more than happy with a low secret solution MuchXS at the moment.

I wish you screwed up something blatantly obvious. Then I'd point it out and your amp would work. Win / win.

Unfortunately there's nothing blatantly obvious.

when I test the output jack there is continuity to grd on both lugs

Got it! You're shorting your output through your impedance selector switch. You should be able to throw the switch the other way and your amp will work.

Run the black wire direct to the jack. Yellow and green go to opposite ends of the switch with a wire to the jack in the middle. Or just bypass the switch. Wire your output straight to the jack and sort the switch out later.


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thanks Muchxs...I figured the way I had the output wires to one side of the switch only just to see if i had sound or not would be the same thing as running the black common and green 8ohm direct to the jack itself...Man, its frustrating knowing it's so close yet can't get that ci-gar lit.....

I wondered if maybe there could be an input or output jack that needed to be insolated from the chassis as some other amp kits have...

All the grounds look ok though ???

what do you think about that 330 ohm resistor and the present voltages?? whats the magic voltage range for these amps to work the best and can i achieve it from installing the right cathode resistor ???

Muchxs, you need a virtual tip jar!
Ernie, your wiring looks really nice. I like the little twisted wires on the ground side of the filter caps; it reminds me of the bumpy myelin sheath on neurons! The little bumps speed up signal transmission in your brain. I kind of had a weird idea of making similar little gaps and valleys in my wiring, although it's probably a lost cause...

Good eyes, much. It can be seen plain as day that the switch is wired to short the black and green OT secondaries.



Ernie,

Fix that switch.

Solder the black wire off the OT directly to the ground tab on the output jack. (Remove it first from the center lug on the switch.)

The green wire on the switch is ok. However, you must remove completely the light green jumper from the switch to the tip of the output jack.

Solder a new jumper from the center lug of the switch to the tip of the output jack.

(No other wires will be soldered to the jack.)

Only these two:

A.) the one black ground wire to the ground lug of the output jack

and

B.) the new jumper from the middle lug of the switch to the hot side - tip - of the output jack

Next, solder the yellow wire from your output transformer secondary (8 ohm, I presume)
to the bottom lug on the switch.

If you do this, you will have switchable 4 and 8 ohm output.

Note: When the switch is up the down side is on. The up side is off.

When the switch is down, the up side is on. The downside is off.

All the grounds look ok though ???

It's done a little different than I would do it but ground is ground. I might send the volume pot ground back to the preamp ground.

what do you think about that 330 ohm resistor and the present voltages?? whats the magic voltage range for these amps to work the best and can i achieve it from installing the right cathode resistor ???

Swap your bias resistor to compensate for supply voltage not vice-versa. We can "adjust" the supply voltage with resistors modded Valve Junior style but it's not the right way to do it.

330 ohms works "for now" but is biased hot. Stick the 470 ohm in there when you get it, you'll have a happier amp in the long run.

This is where we get into the '50s Champ / '60s Champ discussion. '50s Champ is related to Gibson GA-5, little Danelectros, Harmonies and just about every SE 6V6 phonograph amp.

If you take a peek at similar amps you'll see your 330 ohm bias resistor in little Supro and Silvertone amps with plate voltages down around 250v. 470 ohms is about right for the mid-300 volt range. BF / SF Champs should have a 600 ohm resistor IMO. Lotta guys say that sounds too sterile. It is however closer to correct. We can change other stuff to fix "sterile".


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Thought I'd maybe post voltages to see if anything could be out of spec

line 123Vac
heater 6.6 Vac

V1
pin 1 180Vdc
3 1-2
5 181
6 127
8 1
9 5

6V6

3 353
4 304
8 16

5Y3

2 366
4 330
6 330
B+366

2nd E-cap 304Vdc
3rd E-cap 266 Vdc

how do these look to be ?? Thank you

Voltages look fine. Swap that one resistor, that thing should last until the tubes wear out. It might take a couple decades.

Dave, I took everything apart at the impedence switch and ONLY used the terminals on the switch as a point or junction to splice from (basically just to lengthen the leads) to run the 8ohm direct to the output jack to see if it would work or not...I wasn't planning on leaving it that way...will or should it not at least work to test it this way...Like I said it's only wired temporaily..let me know

Thanks Andy..gotta have yer wires twisted :grin:

Well well, i took it apart at the selector switch as per decribed and soldered it up 8ohm only just to see and bingo we have sound... and she sounds pretty good too, maybe not wuite as loud with the 12" C-rex as I thought it might but lots of gain dimed...is this common for these little amps to be pretty quiet on the bright channel up to about 6 on the dial ??

Thank you guys for the help, and besides i'll feel better in the morning for not going to that party tonight anyways...

I'll reread your final post Dave and get that selctor switch sorted out..I will get that 470 ordered up and switch out Much..

http://i271.photobucket.com/albums/jj134/livtohunt60/31.jpg

is this what you're talking about Dave..makes perfect sense how i had it wired that it would short itself out...thank you guys very much again for the help, and umm err Muchxs, recipe ?? :lol:
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tests 0 too
http://i271.photobucket.com/albums/jj134/livtohunt60/30.jpg

That's a 0.1 ohm resistor (aka 100 mOhm.) Just like 2k2 equals 2.2 kilo ohms.

It reads zero ohms because your meter cannot read to that degree of accuracy

Good job "Unca" Ernie. I new if you took that switch out of my 5e3 there would be "Mojo" problems. But I thought it would be in my Amp and not yours. Nice soldering job on all your connections. Your a Rembrandt with a Weller (inside joke).

That's a 0.1 ohm resistor (aka 100 mOhm.) Just like 2k2 equals 2.2 kilo ohms.

It reads zero ohms because your meter cannot read to that degree of accuracy

thanks for the info on the resistor value, but I'm insulted you think my $9.95 multi meter isn't capable of precise measurements.. I won't tell it you said that.. :lol:

Thanks Wiley-C.. After I pulled the zener and the switch, resoldered the centre tap, and plugged yours in, it only smoked for a few minutes, so the mojo is still there.. We both know I'm no Rembrandt with a chainsaw, all i can hope for someday I might get decent with a soldering iron..

... I'm insulted you think my $9.95 multi meter isn't capable of precise measurements..

Heh, no worries. I'd be surprised to find any tube amp hobbyist (ie. anyone who's day job does not involve electronics) with a meter that could accurately read tenths of an ohm.

...is this common for these little amps to be pretty quiet on the bright channel up to about 6 on the dial ??

Yes, mine is quiet till it's around 5 (room level) then it kicks in when you go past 12 o'clock. I have a WGS G10C which doesn't hold anything back. One thing I'd def change in your build is the center wire from the switch to pin 7...shielding wire is the go here

http://i757.photobucket.com/albums/xx217/telenut62/GA-5%20Champ/05052012679.jpg

I've got very quiet 5e3 and 5f2a without shielded wire -- if it's quiet and stable, what would be the benefit?

Keyser...the more I mess with this amp building the more I realize the importance of a better meter....without spending a bazillion dollars what could you suggest me looking at??

Telenut, so it's not something different with my amp then that makes it as quiet as it is then. the little bit I've had the chance to play through it so far, the distorted tones are amazing for the size of it...

We spent all weekend at a Country festival and some of Canadas top players were in attendance and that bright red 5E3 of mine was difficult to hide amongst all the equipment waiting to go on stage....a long time friend who is very well known up here whos played with many big named bands, I asked if he'd play through my 5E3 and doing a sound check revealed we couldn't dial in enough cleans for his tastes with his 64' vintage tele, so it was a short lived boost to my ego when it was pulled off stage to have it replaced with a factory fender deluxe reverb....All therest of the show and last night I'm thinking I need to adjust that amp to get it cleaner because I would love him to own one rather than him lugging heavy amps around everywhere he plays....but he's gotta have reverb so I might need to think of building another circuit for him...

I'll pull that pin7 wire and replace it with a shielded...thanks Tele for that..