Welcome, Guest. Please login or register.
January 19, 2018, 01:13:06 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
|-+  British Style
| |-+  Plexi Lead, Bass, Superlead
| | |-+  Valve questions about 1987.
« previous next »
Pages: [1] Go Down Print
Author Topic: Valve questions about 1987.  (Read 5345 times)
cave.al
Newbie
*
Offline Offline

Posts: 9


View Profile
« on: June 26, 2011, 03:06:23 AM »

Hi all, new to the forum.

I bought a 1987 off a my local forum (AGGH), it's been passed around a few members, so I'm not sure of any mods and such, but I have a few questions all the same.

The day after I got it it blew a HT fuse, I emailed Nik for the correct rating/type, and got a new one. I'm not sure if this has happened before or since, but one power valve looks blown i.e bottle is white in colour and doesn't glow. The amp still works, but would it cause damage to the amp running it on only one power valve?

Also I'm interested in what bran of valves people recommend.

Cheers,
Al.
Logged
wyatt
Guest
« Reply #1 on: June 26, 2011, 09:53:39 AM »

Not good to run it on one tube. 

I don't think there is any immediate danger from it, but it throws everything off...the two tubes work together as a pair. The signal wave gets split and part gets sent to each tube. Think of it like a two cylinder engine.

For modern EL34's, I think the current favorites are SED (Winged C), JJ, and the (Russian made) Mullard EL34.  Here in the states, the SED has climbed up in price, but it is a very reliable and well regarded tube, it would be my pick.

Chances are the power tube going is what blew the HT fuse, I surprised it did not blew the mains fuse.
Logged
ampkits
Administrator
Sr. Member
*****
Offline Offline

Posts: 327


View Profile
« Reply #2 on: June 26, 2011, 01:10:23 PM »



What Wyatt said! Smiley

You must NOT operate it with 1 tube

The white powder thing indicates it's gone, most likely thru breakage (shipment?)

You need to replace (get a matched pair, good ones are at most USD 30 a pair, JJ etc), and rebias the amp with the new tubes.


Thanks!

nik
Logged
cave.al
Newbie
*
Offline Offline

Posts: 9


View Profile
« Reply #3 on: June 26, 2011, 05:11:05 PM »

I was afraid that'd be the answer.

My two main amps are out of action due to power amp valves now (the other being an 18w made from Ceriatone and other bits)

 Cry
Logged
ampkits
Administrator
Sr. Member
*****
Offline Offline

Posts: 327


View Profile
« Reply #4 on: June 27, 2011, 10:18:53 AM »

Hi

Tubes are wearables, same  way your strings are.

You do need to change them from time to time.

And, when you change, some amps do need to be rebiased for the new tubes.

As for the 18W, thats cathode biased amp, just get a matched pair of EL84s.

But all in all, you do have to change the tubes, they wont last forever.

We get the JJs from Eurotubes, and they're pretty much one of the best dealers for JJ, if not the best. Ie, they do test, and match, which is important.

It is important to get tubes from good source. I do hear stories when ppl buy matched tubes from ebay or other online stores, only to discover they're off by 15mA for the bias.

pricier by USD 2-3, but would be better, in the long (even immediate) run.

Thanks!

nik

Logged
cmoore
Sr. Member
****
Offline Offline

Gender: Male
Posts: 366


View Profile
« Reply #5 on: June 27, 2011, 05:50:03 PM »

In my cat biased El84 amps, I have been using TAD. If you can afford two sets (as you have found out, you need spares for just this reason) I would try 2 different brands and see what you think. Don't trick your self into hearing something that is not there. If the difference is not obvious to your ears......don't sweat it.
Take a look at:
KCA NOS tubes
Doug's Tubes
Tube Depot
and the guys from Canada are good also.......The Tube Store
Logged
DaveMcLain
Newbie
*
Offline Offline

Posts: 11


View Profile
« Reply #6 on: July 23, 2011, 09:15:07 AM »

I agree with the earlier post in that you need to buy a couple of pairs and try them to see what it sounds like and what you find that you like best.  The nice thing about the 50 watt head is that you only need two output tubes so it's less expensive to try different things.  Put them in there and bias the amp.

I've experimented with a lot of different output tubes in a 50 watt Marshall and I tend to like the JJ E34L's about the best if you're going to use an EL34.  I tend to like the EH tubes but I don't like their EL34 very much yet their 6CA7 is quite good sounding. 

Logged
cave.al
Newbie
*
Offline Offline

Posts: 9


View Profile
« Reply #7 on: October 04, 2011, 03:28:08 AM »

As closure to this thread I finally got around to getting this amp to a tech.

He said the bias was running at a ridiculously low voltage (mid twenties?) which is probably why the valves and HT fuse blew. Apparently there was a resistor limiting the voltage from anything over 30v, so he changed that and biased to around 35v.
Logged
ampkits
Administrator
Sr. Member
*****
Offline Offline

Posts: 327


View Profile
« Reply #8 on: October 04, 2011, 09:57:59 AM »

Hi Thats cool Al

But biasing cold wont hurt the amp or cause it to blow a tube.

I suspect the tube got hit in shipment, and broke.

Thats what the white powder stuff is.

Anyways do keep us posted on how it goes?

Thanks!

Nik
Logged
plasticvonaband
Hero Member
*****
Offline Offline

Gender: Male
Posts: 767


Pickin and Grinnin since 1989


View Profile WWW
« Reply #9 on: October 04, 2011, 06:04:09 PM »

I agree. Glad you got it fixed. BUT...

The white stuff indicates the tube broke, air got in there, and if it didn't blow when the heater turned on at started warming the cathode and electrons started flying, it certainly did when plates got their juice. Biasing low won't cause that damage, it may make your amp sound like crap, and you may get crossover distortion, in theory, but not blow a tube, in fact it would increase tube life.

Gregg
Logged

Overdrive is like peanut butter. Some like it crunchy, some like it creamy.
Bluesmaster 50 2x12 combo and some guitars.
DaveMcLain
Newbie
*
Offline Offline

Posts: 11


View Profile
« Reply #10 on: November 12, 2011, 09:03:47 AM »

I don't think the amp tech was talking about it being biased cold he was talking about it being biased very hot.  Instead of -35 or so volts on the grid he was only seeing -20's and thus unable to properly bias the tube and reduce it's idle current to an acceptable level. 

Just my thoughts. 

In today's world I've found it to be quite common to have to change a resistor or two in the circuit to allow the bias pot to "scale" correctly for the tube of choice.

Logged
cave.al
Newbie
*
Offline Offline

Posts: 9


View Profile
« Reply #11 on: November 15, 2011, 04:14:54 PM »

Yeah, that's probably it, not being an amp tech myself, I didn't quote him properly.
Logged
Big Twang
Newbie
*
Offline Offline

Gender: Male
Posts: 7


IF IT'S TO LOUD....YOUR TOO OLD!!


View Profile
« Reply #12 on: September 02, 2014, 12:28:14 AM »

go online to one of the upper mentioned tube stores or just good 'ol ebay.

buy your self a set of ELECTRO HARMONIX [EH] 6CE7 tubes and EH 12AX7'S and dont look back.

i have used them all, love many, wouldnt use some for paper weights [jj's come to mind, especially their pre amp tubes] but i can say without batting an eye that when i put my first set of the EH 6CE7/12ax7 in my ceriatone 1987, COMPLETE difference! all those little under tones that i heard from my heroes marshall amps just wasnt there before, no matter what i tried.

then, i put in that set and WHAMO!! there it was. about two weeeks later i find out edward vanhalen had the same issue. he heard that pete townsend used them exclusively in his amps and that is where ed's brown sound made its final touch, the 6CE7's that he didnt reveal until not long ago.

i had winged C EL34's and tung sol 12ax7 in it. GREAT combo also. but the EH combo of 6CE7 and 12ax7 just put the amp over the top and i get EVERY marshall tone from my heroes [the british ones anyways] now.

just do it. then i will send you my info so you can add me to your will.   Grin
Logged

MUSIC is in the ear of the beholder!
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.