RED(plate) ALERT!!!!

v00d00blues79 · Post by **v00d00blues79** » Fri 01/20/06 3:49 pm

Your Voltages should be close to these:

http://www.18watt.com/modules.php?name= ... it&lid=154

blaren · Post by **blaren** » Fri 01/20/06 5:34 pm

Thanks SO much voodoo thats what I needed...ok here are my numbers:
In 36 watt mode they go a little sumthin like this

Pin 3 7 9

V4 11-12 317 320
V5 " " 321
V6 " 320 321
V7 " " 321

In 18 watt mode:

V4 32 350 349
V5 14 349 350
V6 14 349 349
V7 32 349 349

I dont know what its supposed to look like in 18 watt but it looks ok in 36 doesnt it? I guesss I can use it tomorrow?...PLEASE???

v00d00blues79 · Post by **v00d00blues79** » Fri 01/20/06 5:51 pm

well... these are the typical voltages for an 18watt:

http://www.18watt.com/modules.php?name= ... it&lid=118

But what i did see on your voltages is the lack of any real difference in screen to plate voltages... your screen grid voltages should be lower than your plate voltages... somethings not adding up there. I would check your plate resistors to make sure that they are ok. they are typically 100ohm/2w or maybe even 1k/2w...

just my .02

Thanks,
Andy

Post by **Plexi** » Fri 01/20/06 5:55 pm

can you take a picture of the cap can and connections to the EL84s?

It looks like your screens and Center tap of the output transformer are both on the high side of the B+ on the cap can..as the screen and plate voltage is very close to being the same..

Richie

Post by **Plexi** » Fri 01/20/06 5:56 pm

in my 36 watter.. the plate runs about 332.. and the screens about 322.
I think somewhere there is a voltage chart..

v00d00blues79 · Post by **v00d00blues79** » Fri 01/20/06 6:00 pm

Ritchie,

i sent him the the link to the voltage chart.

Thanks,

Andy

Post by **Plexi** » Fri 01/20/06 6:03 pm

DUH...sorry v00d00blues79 .. i was typing the reply,went to grab a coke.. and didn't see you posted about the same time..
yeah there it is..

Richie

v00d00blues79 · Post by **v00d00blues79** » Fri 01/20/06 6:19 pm

it would be nice to see some pictures of the power supply and power amp... its weird, the 36w is the only non-fender amp i feel confident in helping to diagnose problems for... of course its the only amp on this board that i've actually built, but thats another subject entirely.

I've jumped around a bit... 36w was my first build, then a CG-clone, and now i'm working on a TW Liverpool...

Thanks,

Andy

blaren · Post by **blaren** » Fri 01/20/06 7:33 pm

at work right now. Will post pics tonight. So these volatges are a BIT off but you think it's kinda safe??

Post by **Plexi** » Fri 01/20/06 8:25 pm

""So these voltages are a BIT off but you think it's kinda safe??""

Not looking good to me.. the screens are about the same, or a volt or so higher..

For the Plate and screens to be like the voltages shown, would almost have to have both supplies hooked to the same high B+ of the cap can.
At least thats what it looks like to me.

easy mistake if that is it,and easy fix.. we may know more with the pics..
the only other thing i can think of is,,if the 1.5k resistor is 1.5 ohm instead.

safe... not looking good.. kinda like if a doctor told you yor blood pressure was 200 over 180..

OH!!! and at all times have a speaker hooked to the amp when it is on..
and last thing.. keep the volumes down to 0.
An oscilation can make a tube draw too much current..

So we will wait to see what you come up with.. look at the white square resistor on the cap can.. it should be 1.5k and not 1.5 ohm

Richie

blaren · Post by **blaren** » Fri 01/20/06 10:40 pm

cool thanks so much fellas. I did not have the vols at 0. Also, I had the hotplate set to load hooked-up...not a spkr. I'll try both tonight and hopefully things look better. Picas too I hope.

blaren · Post by **blaren** » Sat 01/21/06 3:23 am

5W1K5J so THAT's OK. I'm learning so much more than I wanted to...well so much faster lol.
Yeah now that makes sense...kinda, well I see how you wouldnt want higher voltage on the screen than the plates.
My Son isnt home and he's the camera guy. I HOPE I can get some pics posted early and hopefully it IS just wrong on the cap, and hopefully it IS real easy and hopefully I can have it all squared away before "showtime". If not, I think I'll tell my stupid rhythm section (how smart do you have to BE to pull one-over on a drummer and bass player??) that, like an idiot, I was messin inside my new amp and it fell off the stacks of books and smashed the rectifier tube so I have to use the '73-50W.
It's actually a fair sized room tomorrow (Sat) so things could be a lot worse. BUT...if I can get that thing fixed and let it RUN....oh boy I'll be SOOOO happy.
OK now it's starting to NOT make sense...HOW can the grids have more voltage than the plates?????...Thought I was starting to grasp this "CATHODE" biasing BS....turns out I just got held back about 9 grades!....DOH!!!! I think I better quit thinking and trying to figure this out and just take and post some pics and just be told what to do.
Oh btw, I used real speakers this time (did a re-check) with the volumes off....good boy eh?

Post by **Plexi** » Sat 01/21/06 9:57 am

""" Also, I had the hotplate set to load hooked-up...not a spkr"""

Hotplates are for cooking.. not a fan of those load boxes,i've seen them cook too many amps.
1.5k thats good. And narrows it down.
I think your doing great at figuring this out.

One way is to check the voltage on those 2- 100 ohm resistors [grey looking resistors brown black brown stripes].. that go to pin 9 of the EL84s.. on one side see what the voltage is on the same side the pots are mounted..
And check voltage on the cap can each side of the 1.5k resistor.. and always be careful.

On that cap can..there should be one wire on one side of the 1.5k resistor
the other side will have 2 wires connected.
The OT center tap wire will be on the high side,and the wire to high B+.. on the lower voltage side will be the supply voltage wire to the board and those 100 ohm resistors.

This should tell the tale.

I can see why your amp may have had more hum than what it should have..if this is incorrect hookup.

Now if the hookups are correct..we get into the something weird part..lets hope it don't go there.

Maybe and Mark/Mark/Phil,and any others jump in and give there ideas of what might be happening.

Richie

Post by **Plexi** » Sat 01/21/06 4:09 pm

hopefully we made some progress today..
Looks like Nik used both the choke and 1.5k resistor. So we took out the choke to see what happens..

After blaren posts some voltages.. still the 18/36 switch is or was off some..but that can be lined out i believe.. But i think in 36 mode he will get by tonight..

Richie

blaren · Post by **blaren** » Sat 01/21/06 4:28 pm

Richie thanks...I just got up and took photos. I'll post them here now and THEN I'll re-read and digest your last post and take a look. I'm SO hopeful! I THINK things are looking-up. Here are some pics. Hope they help.
Thanks again...God...I'm SO lucky you guys are here!!!

[/img]

Post by **Plexi** » Sat 01/21/06 4:54 pm

Great pics.. it just kept throwing me off seeing that resistor on the cap can..and thinking of the number of wires hooked to the cap can..
kinda brain freeze.. then it hit me.. i went back looked at your pics you posted when you got the amp to verify the choke sitting on the chassis.

As we worked on the problem.. the voltages in 36 mode are much better,and more what they should be..
But still something funky with the 18/36 switch.. 18 mode one set of tubes just isn't right. but i think Nik can figure this out and do some testing..or look at your amp pics and see something. Should be easy to fix the values or setup to get it going the right way.
But this is a good heads up on the 36.. you use one or the other..choke or resistor.."NOT" both.. and the old layout shows both being used. Which is incorrect. I've been useing just the resistor.. and I'm sure it would be a few dollars cheaper for Nik to use the resistor..over the cost of a choke.
I do like to use a 7 to 10 watt value. The 5 watt should be ok..but it may get pretty warm in 36 mode.. But that is its job.

The new[correct] layout is posted that Pete drew up.

And we may have not seen this if you hadn't posted or asked what was happening..

Richie

blaren · Post by **blaren** » Sat 01/21/06 5:16 pm

Plexi wrote: And we may have not seen this if you hadn't posted or asked what was happening..

Richie

Yeah I'm such a big hero lmao.

One thing you're wrong abut though Richie....EVERYBODY knows that the choke will sound WAY better than the resistor....just LOOK at it!!!
Oh and not only cheaper for Nik but I guess it would be cheaper for the buyer too because of shipping weight....still though...it's WAY sexier looking with the choke...which equals...MOJO, which means,...it SOUNDS way better...c'mon man.
Just a footnote....it sounds just as BETTER using the resistor,...AS LONG AS the choke is still on the chassis.
Anyway yeah...just let me say that this place is the BEST!! OK I buy this amp (cheap) from vietnam or something and it's awesome...then I go and find a "slight" problem with it by accident. My options?...take it to a butcher...I mean a tech who has NO idea....OR....nope that was my only option...yikes. Well I mean I KNOW Nik would bend over backwards to fix whatever but...I think I would have just brought it in somewhere.
BUT NO!!! This place is like a frickin live helpline center or something....awesome!!!!
NEVER have I had a bad experience dealing with people online...buying, selling,,..returns....it seems better than LIVE....well...never have I had a BETTER experience anywhere than here. I mean you Richie but everyone else too. This is crazy....ok I'm tearing-up here so lmao I gotta go to the dump for a minute (not an amp related dump-run).
I appreciate it dudes.

blaren · Post by **blaren** » Sat 01/21/06 8:14 pm

Dad....I mean Richie, Can I PLEASE use it in 18W mode tonight??
I just been thinking....You know how in 18w Ionly have 5V on those 120Ohm resistors right?...which is bad right?...BUT....when it's like that I have like 15 on the 150s...SOOOO
Dont those 2 add-up to enough to run 18Watts? The plates measure about 353 and screens at ~338 (something like that) in 18W mode.
Contrary to your advice and warnings, I'm JUST gonna run it in 18 for a minute and see if I see any color.
Hopefully there wont be any RED...especially on my FACE when I come back and say I blew it up or something.

blaren · Post by **blaren** » Sat 01/21/06 8:29 pm

well that went rather well I think. It looks more normal now (I think) I have no more redplating. When it IS in 18 watt, the 2 outside tubes stay lit but there's no blue dancing out of the plate holes. Kinda like 2 are still just idling. That's kinda what I expected to see in the first place but I dont think it's quite right.
But anyway, it LOOKS and sounds fine in 18 and 36.
I hope someone's still tuned-in and stops me before I either go out and roast something or have WAY too much fun!

Post by **Plexi** » Sat 01/21/06 10:45 pm

The only real way to tell is to check the voltage on the cathode..pin 3 on each set of tubes. and actully see what they measure.
since these resistors go to that switch, and can't see all the wires of how it is wired..That is what i ws going on. By now your probably jammin away..

All the voltages now look much better.. and if you can measure the pin 3..when the amp is in each setting to see what exactly is on those pins..

If you have 11v cathode in 36 mode..and 15v in 18 mode.. then it should be fine..
I still think if Nik had this wired with the choke and resistor..and the voltages on the plates were a volt or so above the plate and pretty high..it would seem he would have taken his readings and calculations for the cathode resistors. Which would be off,compared to how it was then to how it is now. Anyway.. GOOD LUCk at the gig..

Richie

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RED(plate) ALERT!!!!