Very old (new to me) amp

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by DanR, Jan 6, 2004.

  1. DanR

    DanR Member

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    I just received a 1960 Ampeg Jet amp that I won off Ebay. Upon trying it out for the first time, I found that the output was quite lower than what I would expect. My '75 Vibro Champ is louder. On the other hand, the amp is quite quiet hum-wise.

    Upon closer inspection, it appears that all the internal components are original, although it is difficult to tell whether the filter cap can has been replaced. Apparently, it is doing it's job as I've mentioned it's pretty hum-free. The tubes are pretty old, also. They are old American tubes and the power tubes (6V6) are a mixed pair consisting of one Westinghouse and one Motorola. Also, the phase inverter tube is a 6SN7 as opposed to the specified 6SL7. The internal resistance of these tubes is considerably different. I looked the specs up last night.

    Anyhow, I'm wondering if the lack of power is due to old tubes or if the fact that the wrong PI tube is used is the cause. Also, should I automatically have all of the electrolytic caps changed? Are there any other components I should consider replacing?

    DanR
     
  2. Swarty

    Swarty Member

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    The 6SL7 has substantially more gain than the 6SN7, so that may be at least part of what is going on....

    When I saw DanR from St. Claire Shores in the amp tech forum I figured you were Danny Russell (Blitz Amps, designer of the Naylor Super 60)....guess not, eh? I know he's been up there for about a year or so now....So if you really want to get the amp up to snuff, he'd be real handy.
     
  3. DanR

    DanR Member

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    I'm Dan Rice. Actually, the last time I checked, he (Danny Russell)had a little shop about a mile away from me. If he's still there, I'll give him a call.

    Thanks,
    DanR
     
  4. RupertB

    RupertB Supporting Member

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    Dan,
    Regarding the cap can: Most caps and cap cans have a four digit date code that reads wwyy (ww being the week of manufacture (1-52) and yy being the year).

    If your can has (for instance) "3457" on it (34th week of 1957) I'd bet its original. If it says "4189", It probably got recapped in the early '90s.

    If they are original, I'd have them changed (the electrolytics). I agree with Swarty, that PI is at least part of your problem.

    Good luck.
     
  5. DanR

    DanR Member

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    Thanks guys,

    I did not know about the date codes on cap cans. That should be particularly helpful. I don't want to change the can if it is fairly new. As I mentioned above the amp IS very quiet hum-wise.

    DanR
     
  6. DanR

    DanR Member

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    This is an update of my '60 Ampeg Jet saga. I dropped the amp off to Danny Russell (Blitz Amps) per the recommendation of Swarty. I picked it up 3 days later and it is almost an entirely different amp. Danny play- tested it prior opening it up and had a pretty good handle on what was going on with the amp. A number of caps, a new speaker (Jensen C12Q) and some cleaning and tightening and the amp sounds great and plenty loud!

    Danny loves to talk and is great at explaining what is happening with the various components in the amp. So, I not only got my amp repaired, I got an education, too.

    Thanks for the recommendation, Swarty. If any of my fellow Michigander forumites need amp service, I highly recommend Danny.

    DanR
     
  7. Swarty

    Swarty Member

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    Danny gets the eastern Michigan guys (including Detroit). I get the rest :D
     
  8. thesedaze

    thesedaze Member

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    That speaker gave it a 'loudness' boost I'm sure. The original speaker is a P12R, I believe, which rates 25W, the current speaker pushing 35W, plus it being ceramic. Btw, how do you like the ceramic speaker? Do you find it musical enough for that low wattage amp? Have you tried pushing a Celestion Blue in there at all?
     
  9. DanR

    DanR Member

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    Actually, the original speaker was a P12S, which is even lower power handling. I had not even heard of a P12S until I got this amp. So far, the tone is fine. I imagine that the tone of the speaker will change a little due to breaking in, but I'm happy with it. If I ever get a "Blue", I'll definitely throw it in there to check it out.

    DanR
     

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