First power up problem... (Solved)

Chris Brown · Post by **Chris Brown** » Mon Sep 12, 2011 10:35 am

I finally completed my trri to ods conversion... this is my first build.

When I power with a 100 watt bulb it glows dim so I think thats about right...?

The bulb doesn't temporarily brighten when I switch from stby to on like I read it might..it just stays steadily dim... is that bad?

Here's what's happening...

When I measure from chasis to the rectifier output or ps filter caps I get about 1 volt when I first switch the power on and then that quickly drops to negative milivolts and eventually sits about -500mV.

I get negate millivolt readings on the plates too.

I wired the mains like this...
mains neutral > fuse > pt white
mains hot > power switch > pt black

I wired rectifier like this....
(pt secondaries > 1n4007s) > standby sw > ps filter caps/ot red/choke...

I guess I picked that up off of a ceriatone layout... the known 124 schematic has the voltage hitting the ps caps before the standby sw... should I rewire this or is my wiring ok?

the pt is from a 65 twin reverb reissue.. the secondaries are red/red to rectifier, green/green to heaters, and brown/brown one to ground and one to bias

I get about 280vac measured between the pt's two red secondary wires... the 1n4007s are correctly oriented... do I have bad diodes?

The bias secondary seems right. The heaters are 6Vish. Seems like the problem is somewhere between the the hv secondaries and the standby switch which I checked for continuity and it was in order.

Thanks in advance for any help.

Best, CB

DonMoose · Post by **DonMoose** » Mon Sep 12, 2011 12:59 pm

[edit] decided I wasn't actually helping.

butwhatif · Post by **butwhatif** » Mon Sep 12, 2011 1:34 pm

Sounds like u r lacking the ground reference of the hv bridge rectifier, since there is no ct, u have to use a fw bridge, did you do that?

Chris Brown · Post by **Chris Brown** » Mon Sep 12, 2011 1:48 pm

butwhatif thank you so much for the help!

I just used a fw rect like on the 124 schem thinking that it was going to magically work... didn't even think about the missing ct on my transformer... makes total sense to me now that you point it out.

Is there a secret h.a.d. mojo fwb circuit or can I just use a standard 4 diode fwb circuit?

Structo · Post by **Structo** » Mon Sep 12, 2011 2:11 pm

Some of us like to use fast recovery diodes for the rectifier.

You should wire your primary like this.

mains hot > fuse > power switch
mains neutral > pt white

butwhatif · Post by **butwhatif** » Mon Sep 12, 2011 2:56 pm

u should be able to use a standard fwb-wire it like the fender 65- a link to the sch and manual
http://www.studiosoundelectronics.com/s ... manual.pdf

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 1:42 am

ok fwbridge rectifier helped... I think...

now I'm getting ~265Vdc out from the rectifier... I've triple checked my wiring... is there something obvious?

ToneMerc · Post by **ToneMerc** » Tue Sep 13, 2011 1:53 am

Chris Brown wrote:ok fwbridge rectifier helped... I think...

now I'm getting ~265Vdc out from the rectifier... I've triple checked my wiring... is there something obvious?

Is that with the standby switch open or closed?

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 1:57 am

both... when standby is set to power I get the same 265ish reading at the ps filter caps

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 2:03 am

btw this is through a bulb limiter... tubes in and speaker connected

ToneMerc · Post by **ToneMerc** » Tue Sep 13, 2011 2:08 am

Chris Brown wrote:btw this is through a bulb limiter... tubes in and speaker connected

Remove the bulb limiter

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 2:15 am

I knew it was something obvious..

LOL I'm such a newb..

Thank you so much!!

ToneMerc · Post by **ToneMerc** » Tue Sep 13, 2011 2:27 am

Chris Brown wrote:I knew it was something obvious..

LOL I'm such a newb..

Thank you so much!!

YW, not a problem

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 3:53 am

Thank's to this forum my amp passes signal... the controls work... sounds like it's going to sing.

I've been luring since last year and slowly learning and assembling the boards for this build... in the last two weeks I've finally wired it all together... Big thanks to everyone here that ever asked a question or gave an answer!

Here are my voltages... looks like I need to adjust the dropping string a little bit...

I'm getting 440 at the plates
295 / 285 at the pi
192 on v2
191 on v1

At the lowest setting the bias mv readings are pretty high... I don't have a matched quad of 6l6s

for v4 and v5 I have jj6l6gc that measure 29mv and 37mv

for v6 and v7 I have sed winged C's in there that are measuring 48mv and 44mv... that's probably too hot... I have a pair of junk gts that I can try also...

is it normal to get these readings at the lowest bias setting?

Chris Brown · Post by **Chris Brown** » Tue Sep 13, 2011 5:50 am

gts were very close to the jjs... still bias mid 30s at lowest setting though... amp sounds great

Tube Amp Archive

First power up problem... (Solved)

First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)

Re: First power up problem... (Solved)