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re-tubing an Amo

Discussion in 'Amps and Cabs [BG]' started by Lightngsvt, Jan 20, 2001.


  1. Lightngsvt

    Lightngsvt

    Jan 13, 2001
    I have a 1969 Ampeg V4-B 100watt bass amp/head. I am the second owner, I got it form its original owner about 2.5 years ago. I also have an SWR Workingmans 12 for a practice amp and am falling in love with the SWR sound.

    Anyway, I think my trusty AMpeg may be due for a re tube and I want to give it a fair chance before I sell to get an SWR Bass 500, or MOBass head/amp.

    Does anyone know what type and quantity the tubes are in this amp? WHere can I go for info? Where can I buy tubes for this amp? Any info is greatly appreciated!
     
  2. Bob Gollihur

    Bob Gollihur GollihurMusic.com

    Mar 22, 2000
    New Joisey Shore
    Big Cheese Emeritus: Gollihur Music
    I've had good luck with Lord Valve (NBS Electronics) for various preamp tubes (Eden, Kern) and trust his judgement. In fact, I just told him what I needed for my Kern last week and let him make the best choices. I also bought an RNC compressor and QSC power amp- his prices are good. If you ever check out the alt.guitar.amps newsgroups, he is a highly respected and very vocal no-BS influence.

    http://lord-valve.freeyellow.com/ is his web site, but your best bet is to just call him at 303-778-1156 after 1 PM Denver (Mountain) time - he's a busy guy, and you will get better response via phone than email.

    He includes a diskette with tube purchases these days that includes his catalogs, various circuits, instructions for biasing new power tubes (which you will have to do) -- and if you ask, he will send matched pairs of power tubes (which can be important), and will test tubes in amps/preamps before sending them.

    I just visited the Ampeg site at http://express4.expressivetek.com/ampeg/index.html
    and found an online owners manual for the V4BH, which indicates it takes three 12AX7, one 12AU7, (both types are preamp tubes) and four 6L6/5881 (power tubes). All are common types.

     
  3. Bob Gollihur

    Bob Gollihur GollihurMusic.com

    Mar 22, 2000
    New Joisey Shore
    Big Cheese Emeritus: Gollihur Music
    Also a good resource: http://users.aol.com/bluemuse/ampeg.html
    which is a vintage Ampeg site --

    They have schematics for the V4B preamp and power amp sections (under Schematics)

    Seems the old V-4B preamp section takes two 12AX7 and one 12DW7 (odd, but in LV's catalog) and I am unclear as to the fourth - 6K11 (???)

    The power section uses four 7027A.

    BTW, I do have an email from Lord Valve with his preamp tube catalog as of Dec., but trashed the power tube email. Maybe someone on TB has one - email me if you want a copy of the preamp one.
     
  4. If you are gonna retube you also need to consider getting the amp checked out by a tech, there are some comp[onents in amps of thet era that are starting to leak and can cause some pretty major problems even meltdown.
     
  5. Lightngsvt

    Lightngsvt

    Jan 13, 2001
    Thanks for the help guys! I am a newbie to working with tubes. So what is a "normal" interval to re-tube an amp? What are good brands of tubes to use? I use the amp for about 4 practices a month and 1 - 2 gigs a month. Right now it just seems to have lost its punch and sounds a bit "distorted" (pushing 4 ohms through 2- SVT410 pro cabinets, bought new in 1996 and all my basses, except my Ric 4003, are active pre-amp (Music man Sterling and Warwick FNA)and seems to be developing a tiny bit of hum and some hiss.

    Bob Golliur- You said: "which indicates it takes three 12AX7, one 12AU7, (both types are preamp tubes) and four 6L6/5881 (power tubes)."
    and "Seems the old V-4B preamp section takes two 12AX7 and one 12DW7 (odd, but in LV's catalog) and I am unclear as to the fourth - 6K11 (???)
    The power section uses four 7027A." So which do I really need? It looks like the original owner used some of the tubes you mention for the V4-BH, because he has written some of those same tube numbers over the original tube numbers on the back of the amp. IS this good/safe to do? I went to the Ampeg site and was unable to find any info on Vintage gear. Although the un-offical site did have a schematic for a 71 V4-B.

    PLease e-mail me a copy of that catalog.

    I have learned alot already from looking at the sites you recomended!

    BassBrad- I agree its best to let a qualified tech handle the job. Anyone know of a good tech in MI?

    Throbbinnut- thanks for the link.
     
  6. I have a V-4 (Guitar model VT22) head and Psycho helped me out. Thanks Psycho. He advised me to get a cap job and I did. The amp sounds killer! I didn't even need to replace the 7027A's. They're OK A tech can advise the condition of the tubes. Thanks to all tube Gods.
     
  7. I was also gonna mention that the tubes are probably fine if they are 7027A's. I thought mine needed to be changed 9 years ago, bought a quad from Audio Glassic for $100, plugged them in, no difference. Still using that quad today. I have since replaced the load of electrolytic capacitors, though.

    Chris
     
  8. Lightngsvt

    Lightngsvt

    Jan 13, 2001
    Thanks for the advice Psychobassguy and everyone else. I figure if I need tubes, Im looking at about $100 - $120. What should I expect to pay for the lab to install and bias them? What kind of $$ am I looking at for cap's and labor? Not that Im cheap, or cant afford it, but I dont know if I really want to put $500 or more into this amp (when a new SWR Bass 500 can be had for $1100).

    Can anyone recomend a tech in Michigan? Or know of a way I can find a good amp tech?