Broke. Retubing my Ampeg without a tech?

bassbombs84 · #1 09-18-2011, 01:47 PM

So, I have a 70's V4-B that needs a full retube. I can swing the $170 for tubes, but the extra cash for the tech (as well as the wait) is hard to scrape together at the moment. I feel like this is a good time to get my hands dirty and do it myself. I have basic electrical tools (multimeter/soldering iron). Anyone know a good guide for retubing and biasing a fixed bias tube amp?

RickenBoogie · #2 09-18-2011, 01:54 PM

Not a good idea, imo. There's so much more to it than just popping in new tubes. I'd wait till you can afford the tech- and be sure the amp is taken care of properly.

bassbombs84 · #3 09-18-2011, 01:59 PM

I understand the risks. Any good books or links for someone looking to learn? If its over my head then I will seek help or take it in.

JimmyM · #4 09-18-2011, 02:01 PM

How do you know it needs a full retube? Have you had the tubes tested? A lot of times people think their amps need fully retubed when they might just need to replace one. I didn't replace a tube in my V4B the whole time I owned it, which was about 12 years, and neither did the previous owner, who was my cousin's ex-husband who bought it new.

Mr. Foxen · #5 09-18-2011, 02:07 PM

Thinking something needs a full retube is the first sign you don't know enough to know if it needs a full retube or not.

Pilgrim · #6 09-18-2011, 02:15 PM

Posts above ask the right question: HOW do you know it needs to be re-tubed??? What's the problem you are trying to solve??? Tubes last for DECADES. Chances are very small that the problem is a tube.

Interesting responses. In the 60's we went down to the grocery store carrying the tubes we had pulled out of the radio or amp, stuck them in the tube tester which every store had sitting in front, opened the cabinet and pulled out whatever tubes we needed - carried them to the checkout counter and paid for them.

No tech, no adjustment, no nothing. Unplug and replace.

As it happens, I have two tube testers in my basement, and a small supply of 6L6GC tubes. When I need one I just test it and install it.

I think sometimes people make too much of this. If you're installing the tube which is called for by the manufacturer, I would not hesitate to install it yourself. Just find someone with a tube tester and make sure it's the right tube.

Let the flaming commence.

bassbombs84 · #7 09-18-2011, 02:16 PM

Well I bought it used from a friend who had it sitting in her basement for an unknown amount of time. That was about 6 years ago. Since then I have used it extensively in a hard rock n roll setting at full overdrive and have only changed one 12ax7. I am now starting to get a funky overdrive/hiss if I dont let it warm up for a while. I'm hoping its just the tubes and not something else. I figured I could start with them first and if it fixes the problem then great.

**B-string** · #8 09-18-2011, 02:18 PM

The V4B can only be re-biased by changing components unless someone added a bias adjustment pot. NOT a novice DIY project in ANY way.
Make sure you need new output tubes first, 12AX7s, 7025, 12DW7, 6K11 and 12AU7 can be replaced by DIY (no bias required as they are self bias circuits). If you spend the money on tubes only to find out it needs a cap job........your going to be twice as broke!

Pilgrim · #9 09-18-2011, 02:19 PM

Quote:

Originally Posted by bassbombs84

I'm hoping its just the tubes and not something else. I figured I could start with them first and if it fixes the problem then great.

You have it exactly backwards. You should spend a few bucks to have a tech check it before replacing anything.

For that matter, you should carefully unplug and re-plug every tube before you do anything else. Might just be a bit of oxidation on the tube contacts.

BassmanPaul · #10 09-18-2011, 02:22 PM

I'm going to agree with everyone who recommended the tech route. Throwing money at a problem is an unlikely way to fix your amplifier. It NEEDS some TLC from a qualified tech who can isolate what is actually wrong with your amp.

**B-string** · #11 09-18-2011, 02:24 PM

Quote:

Originally Posted by Pilgrim

Posts above ask the right question: HOW do you know it needs to be re-tubed??? What's the problem you are trying to solve??? Tubes last for DECADES. Chances are very small that the problem is a tube.

Interesting responses. In the 60's we went down to the grocery store carrying the tubes we had pulled out of the radio or amp, stuck them in the tube tester which every store had sitting in front, opened the cabinet and pulled out whatever tubes we needed - carried them to the checkout counter and paid for them.

No tech, no adjustment, no nothing. Unplug and replace.

As it happens, I have two tube testers in my basement, and a small supply of 6L6GC tubes. When I need one I just test it and install it.

I think sometimes people make too much of this. If you're installing the tube which is called for by the manufacturer, I would not hesitate to install it yourself. Just find someone with a tube tester and make sure it's the right tube.

Let the flaming commence.

I actually don't diagree, just that NP tubes are not as tightly controlled as the old days and to get peak performance adjustments may be needed.

Quote:

Originally Posted by bassbombs84

Well I bought it used from a friend who had it sitting in her basement for an unknown amount of time. That was about 6 years ago. Since then I have used it extensively in a hard rock n roll setting at full overdrive and have only changed one 12ax7. I am now starting to get a funky overdrive/hiss if I dont let it warm up for a while. I'm hoping its just the tubes and not something else. I figured I could start with them first and if it fixes the problem then great.

Look elsewhere than the big output tubes, sounds like preamp or driver tube (probably the 12AX7 you replaced before

).

bassbombs84 · #12 09-18-2011, 02:25 PM

Thanks for the advice pilgrim. I'll try that. This is an area of interest for me, I have taken a circuits class and have friends/teachers who can help. Just looking for some info to get a jump start.

Pilgrim · #13 09-18-2011, 02:25 PM

Given the fact that it has been sitting, it's probably smart to have a tech check it anyway. Hopefully just re-inserting the tubes will help. If not, it's tech time. It may turn out to have a bad tube, but given their prices today, you don't want to replace any that you don't need to.

Sometimes powering up an amp after it has been sitting for years can cause cap problems, but you're way past being careful about that if you have been playing it for a while.

bassbombs84 · #14 09-18-2011, 02:26 PM

Recommend tube amp technician books???

Pilgrim · #15 09-18-2011, 02:29 PM

Not a clue here!

bassbombs84 · #16 09-18-2011, 02:30 PM

I mean, how did you all learn? EE's all around???

**B-string** · #17 09-18-2011, 02:31 PM

Quote:

Originally Posted by bassbombs84

Recommend tube amp technician books???

Google is your friend, many resources out there.

bassbombs84 · #18 09-18-2011, 02:33 PM

Many, many, many resources. Just looking for a recommendation, sorry.

dsanders · #19 09-18-2011, 02:34 PM

To answer your question, Google it and grab the text you need off Amazon.

BassmanPaul · #20 09-18-2011, 02:35 PM

Quote:

Originally Posted by bassbombs84

Recommend tube amp technician books???

You can gain insight by reading but it's more useful to be taught. A tube amp is a dangerous beast when you have an open chassis. You may inadvertently touch something that will be the last thing you touch apart from the floor!!

Take it to a qualified tech and ask if he would allow you to observe. Some of we older folk would like to pass on what we have learned during our lifetimes.