Welcome, Guest. Please login or register.
Did you miss your activation email?
March 29, 2024, 04:40:14 AM
Home Help Search Login Register
News: Ceriatone Forums are up and running!!!
 
Guests please register
Note: If you want to help you can donate to keep the forums alive.



Do you want to advertise on this forum ? Send me a private message.



Amplified Parts
+  Ceriatone Forum
|-+  Muchless
| |-+  DC 30
| | |-+  Red plating?
« previous next »
Pages: [1] Go Down Print
Author Topic: Red plating?  (Read 10707 times)
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« on: September 12, 2011, 01:13:47 PM »

Hey Guys,just finished my dizzy 30 kit last night. After fire up the second power tube,from the right (looking at the amp from the front) is red plating,gonna spend some time looking at it tonight,but any suggestions where to look first,to save me some head scratching? Also might add that I didn't have the rectifier tube/s on hand but did have the Weber copper cap gz34 solid state equivalent,would that have anything to do with it,and also if you can use the 2 5v4's,or the 1 gz34 does it matter which socket the 1 gz34 would have to go in,it doesn't appear it does,but? ,thanks in advance   Huh?
Logged
wyatt
Guest
« Reply #1 on: September 12, 2011, 01:40:11 PM »

Rectifier socket does not matter, they are wired in parallel.

As for the rest, it could be several problems, considering it's a newly assembled kit.  We start with reading voltages.  What is the B+ coming off the copper cap? And what is the voltage between pins 7 and 3 on the EL84 tubes ("Actual Plate Voltage")? And what is the voltage across the cathode resistor?

Everything else stock to the layout?
Logged
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« Reply #2 on: September 12, 2011, 03:16:41 PM »

Wyatt,thanks. I will check the voltages tonight. Yes I always do my builds stock first.It was late, so I didn't even swap out different tubes. Would the copper cap effect anything,doesn't that give you a higher b+?
Logged
wyatt
Guest
« Reply #3 on: September 12, 2011, 03:32:08 PM »

Wyatt,thanks. I will check the voltages tonight. Yes I always do my builds stock first.It was late, so I didn't even swap out different tubes. Would the copper cap effect anything,doesn't that give you a higher b+?

It should not.  The copper caps are designed to give a similar voltage drop and current to their vacuum tube equivalents.  A WZ34 should perform the same as a GZ34, except they don't have any filaments, so they don't require a 5V supply (but can be used in place of tubes that do).

Vox and Matchless are famous for running tubes hot and killing them young, but tubes don't red-plate until they are near 200% dissipation...which is too high.
« Last Edit: September 12, 2011, 03:34:22 PM by wyatt » Logged
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« Reply #4 on: September 12, 2011, 08:43:51 PM »

Well got home and had a chance to mess with her. Before I did anything I swapped out tubes,this helped dramatically(but still had a small glow).Also when I was tinkering last night I had it on half power,so I switched it to full power today and that takes away any glow at all,and everything's working as it should (also had a brand new bad jj ef86). So I only get the glowing (no where near as bad as last night) when its on low power? I did notice my hi/low power switch is wired upside down, as when its switched to the low setting(going by the face plate) its actually the hi setting. The hi/low switch works as it should,it just doesn't correspond with the face plate. Is the small glowing normal when on the low setting,possibly?
Logged
wyatt
Guest
« Reply #5 on: September 12, 2011, 10:33:48 PM »

I bet it's an issue with the switching of the cathode-bias resistor(s) and the High/Low switch.

It's designed so that when you are in High (4xEL84), you should be running only the 62-ohm, 10-watt resistor. 

When in Low power mode, the switch "turns off" two EL84s and it adds the extra 68-ohm, 10-watt in series for a total resistance of 130 ohms to rebias. 

Sounds to me like the latter isn't happening...it's turning off the two tubes, but not changing the cathode-bias resistance.  It probably is a problem with the switch wiring since you said it was working upside-down.  You may even have it working in reverse.


[edited from before]

You shouldn't even need to power up to check it.  Looking at the Ceriatone Layout, check the resistance between 1.) where "O" connects to the 62-ohm resistor  and 2.) Ground.  You should have 130 ohms in Low switch position and 62 ohms in the High position.
[edited from before]
« Last Edit: September 12, 2011, 11:52:43 PM by wyatt » Logged
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« Reply #6 on: September 13, 2011, 01:45:08 AM »

Wyatt,do you think not having the #9 pin coming out of the said tube would do this?  Shocked  After checking out the inside of the chassis,I went to put that tube back in and noticed that. Tried a new tube(although not a matching one) and the issues have gone away,I will check out the ohm's on the resistors you mentioned,as the switch is still working like it did. I think I'am done with J J's, many thanks
Logged
wyatt
Guest
« Reply #7 on: September 13, 2011, 03:42:22 AM »

Wyatt,do you think not having the #9 pin coming out of the said tube would do this?  Shocked  After checking out the inside of the chassis,I went to put that tube back in and noticed that. Tried a new tube(although not a matching one) and the issues have gone away,I will check out the ohm's on the resistors you mentioned,as the switch is still working like it did. I think I'am done with J J's, many thanks

It's possible, it means you are getting no screen voltage on that tube.  But the affect should be triode mode, which wouldn't necessarily cause red plating and shouldn't affect the other tubes.

Check those resistors; then measure everything I noted above and calculate dissipation...
http://www.webervst.com/tubes1/calcbias.htm
Logged
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« Reply #8 on: September 13, 2011, 10:05:54 PM »

HHMM,checked the resistors,and Iam getting 128 ohm's on both high and low. But the switch is def. working as you can tell from the difference in sound/volume when its switched? Probably a stupid question,but if you are looking at the ceriatone layout,is the "O" on the hi/low power switch on the bottom or top of the switch?
Logged
wyatt
Guest
« Reply #9 on: September 13, 2011, 11:07:58 PM »

HHMM,checked the resistors,and Iam getting 128 ohm's on both high and low. But the switch is def. working as you can tell from the difference in sound/volume when its switched? Probably a stupid question,but if you are looking at the ceriatone layout,is the "O" on the hi/low power switch on the bottom or top of the switch?

Well, it has to do TWO things...turn off two tubes and rebias. 

Here's a pic of an UPSIDE-DOWN chassis...

<<<<<  CHASSIS BOTTOM >>>>>>

<<<<<  CHASSIS TOP >>>>>>

So, the "O" is the top of the chassis, closest to the tubes (directly behind the word LO).

Note on the layout, where it says Chassis Bottom below the switches on the layout.  If you have reverse the wiring, you should probably check your speaker switch as well.

Here is a schematic...
http://www.prowessamplifiers.com/schematics/post/matchless_dc30.pdf

Note what happens at switch behind the power tubes.  In "Hi", it connects both X and Y to the Cathode resistor/capicator, turning on all the tubes...and it sends them out through the 68-ohm resistor to ground.  In "LO" the circuit Y cathodes are disconnected and the outer tubes are taken out of use, plus it forces the X tubes cathode through the 68-ohm resistor before it reaches the 62-ohm resistor and then goes to ground.

« Last Edit: September 13, 2011, 11:13:38 PM by wyatt » Logged
pepper
Newbie
*
Offline Offline

Posts: 21


View Profile
« Reply #10 on: September 14, 2011, 12:20:29 PM »

Yep that was it,the switch was wired wrong (I must have missed the chassis bottom) but that took care of it. I also rewired the speaker phase switch. Man what a great sounding amp,and I dont even have a matching set of power tubes in  it yet! Wyatt,thanks for all your help    Chair Dance
Logged
Pages: [1] Go Up Print 
« previous next »
Jump to:  


Login with username, password and session length

Powered by MySQL Powered by PHP Powered by SMF 1.1.12 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!

CeriaTone Forum is not afiliated with Ceriatone Amplifications. The CeriaTone and name, logo and related trademarks and service marks, owned by CeriaTone. , are registered and/or used in the U.S. and many foreign countries. All other trademarks, service marks, and trade names referenced in this site are the property of their respective owners.