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Magnatone 260 - What to recap and what to leave alone
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Old Black



Joined: 18 Jan 2006
Posts: 1977
Location: Minneapolis

PostPosted: Fri Apr 15, 2016 9:50 am    Post subject: Reply with quote

Bootsypratt wrote:
I totally leave it as is. I would find a new handle, maybe a new old handle, and just maintain the tolex that is left and stop any more from coming off.


completely agree! Looks shockingly like my 280.
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WildIowa



Joined: 06 Mar 2004
Posts: 490
Location: Henderson IA

PostPosted: Fri Apr 15, 2016 5:27 pm    Post subject: Reply with quote

I especially like the look of that power tranny. Pretty massive for the size and layout of the amp. They invested in some pretty good iron back then.
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Sat Apr 16, 2016 8:01 am    Post subject: Reply with quote

I think it looks beautiful as it is; it's not in exceedingly bad condition as these things go.

Too bad on the vibrato. Let's do the simple things first.

A few things to work through--

1) the vibrato should work (as you said, on channel 1 ONLY) with no footswitch plugged in. Did you try it with no footswitch?

2) Also try replacing V2 12AX7. One triode of this tube is also a part of the vibrato circuitry and if half of this tube was bad, the vibrato would not work. It's the LFO (low frequency oscillator) that actually controls the wiggle, so, you know, pretty important! Smile

3) clean and re-tension the sockets for the 6CG7 pair for sure. If someone stuck a 12AX7 in there, that probably means it sat for awhile with NOTHING in the socket. I wouldn't imagine someone would pull a long 6CG7 and stick a 12AX7 in there thinking it would work. Far more likely that the socket sat empty for awhile, amassing corrosion, and then years later someone saw an empty slot and wrongly assumed it was a 12AX7. Use contact cleaner only, not cleaner-lubricant.

4) make sure the ground connections on the cathode resistors of V2 and the two 6CG7s are all solid. Any ground connection in the vibrato circuit should be double checked for continuity to chassis with a meter.

5) Since there appear to be no electrolytic caps in that part of the circuit, I'd be inclined to suspect something other than caps. One thing I WOULD check, though, is the values of the .01, .01, and .022 caps between the grid and plate of V2A. V2A appears to be the oscillator, and if those caps drift too far out of whack on the high side, it can cause the LFO to stall. If your multimeter has a capacitance reading function, it wouldn't hurt to poke around some of the other film caps and look for anything funny. I think they should all be blue Mallory mylar caps (hot dog shaped) most likely, and these almost never fail and should probably be left alone unless there's a compelling reason to suspect them. But anything that looks like a paper-in-wax cap could probably be replaced as preventive maintenance.

6) The next step after all of the above would be to check voltages against the schematic. If all looks relatively normal there, it might be time to take it to a tech, and hope your varistors are OK.


If we were a betting market, the most favorable odds would be on corrosion on the 6CG7 tube socket(s) with V2 12AX7 close behind.


Let us know how it turns out!!
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Mr. Clevername



Joined: 08 Dec 2006
Posts: 2450
Location: San Francisco, CA

PostPosted: Sat Apr 16, 2016 12:10 pm    Post subject: Reply with quote

Don't do this.



The pictures don't do it justice, it was kind of an underwater green. This is how my 450 came to me, and how I sold it.
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Kregg



Joined: 22 Apr 2008
Posts: 3334
Location: Atlanta

PostPosted: Sat Apr 16, 2016 12:20 pm    Post subject: Reply with quote

DO NOT DO IT!
Unless, you completely restore both the amp and the cabinet.
All or not at all. Cool
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Mr. Pumpkin



Joined: 05 Dec 2008
Posts: 1414
Location: Richmond, VA

PostPosted: Mon Apr 18, 2016 8:15 am    Post subject: Reply with quote

First of all, a big "not no, but hell no!" to doing what Mr. Clevername is showing in that post. That's just murder to an amp like this to cover it with something like that. With as many posts as are saying to leave it alone, that's going to be the plan. I'll clean up and firm up what's there and call that good. Why make myself any more work if it's not going to help the value.

Secondly, I will check those sockets and get my cleaner out and hit them good. I did change out V2 as a precaution as well, seeing it was in the vibrato circuit. Will also check the grounds on the cathode resistors. I think my multimeter has capacitance reading on it, so I'll check those caps out as well.

To me, in the case of the caps, it looks like I do have electrolytics in that circuit in my amp. They don't look like the blue Mallorys that most people show, and look just like the paper in oil caps used in the filter caps. Will attach a picture of what I think is caps for that circuit to get your opinion.
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tangelolemon



Joined: 26 Jan 2009
Posts: 2691
Location: Brooklyn, NY

PostPosted: Mon Apr 18, 2016 9:01 am    Post subject: Reply with quote

hmm... that, plus the other tube, makes me wonder if someone modified the amp at some point.

Pics will tell the story, I bet!
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Mr. Pumpkin



Joined: 05 Dec 2008
Posts: 1414
Location: Richmond, VA

PostPosted: Mon Apr 18, 2016 9:07 am    Post subject: Reply with quote

I don't think it was ever modified, unless someone did it back in 1960. Components look too old and original.
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ajeffcote



Joined: 09 Nov 2009
Posts: 2184
Location: Baytown,Tx

PostPosted: Fri Apr 22, 2016 4:35 pm    Post subject: Reply with quote

Wheres the gut shots? Sad
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Mr. Pumpkin



Joined: 05 Dec 2008
Posts: 1414
Location: Richmond, VA

PostPosted: Fri Apr 22, 2016 5:01 pm    Post subject: Reply with quote

Sorry, had to work the past few nights. Coming soon....
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