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Old 17th March 2007, 11:26 PM   #11
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I picked up an old Magnavox console for the speakers and when I removed the back I found this tube amp. Powered it up and listened to FM. Sounds ok. Thinking I should postpone the speaker project and restore the amp. I found the same amp on ebay. It is a 1962 6BQ5/EL84. Would this make a decent amp? Can't see in picture but the amp has 7 tubes. The one in the picture, 4 in a row and 2 smaller in front of the 4.

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Old 18th March 2007, 12:06 AM   #12
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It would make a nice one.
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Old 18th March 2007, 02:11 PM   #13
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Thanks, I think Iíll give it a go. Can anyone provide advice on restoring this amp? The amp has 4 6bq5 and 2 6eu7. The amp produces sound in the console but one 6bq5 doesnít glow and I didnít notice any glow in the 6eu7s (might have been to much dust to notice). I would like to add a power switch to the amp and use it with my solid state Hafler DH 101 until I can get a tube preamp.

Questions:

1) Should I replace all 4 6bq5 tubes?
2) The one 6bq5 tube that is burnt is a Magnavox tube but looks different than the other 3. Could there be a problem that caused this tube to go?
3) What if any caps should I replace? There are 2 caps under the chassis but they look like film caps.
4) Should I replace the input plugs and speaker terminals?
5) Would it be better to add a pot to the amp and use without preamp? I rarely use my turntable.
6) What does the hum pot do?
7) How do I determine the wires for the on off switch?[IMG]http://[/IMG]
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Old 18th March 2007, 02:12 PM   #14
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Another Pic
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Old 18th March 2007, 02:20 PM   #15
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One more Pic
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Old 18th March 2007, 04:12 PM   #16
radtech is offline radtech  United States
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Looks just like the one I have, I posted some pics and a schematic a while back:

Maggie refurb project

I'm still gathering up some parts and trying to find the time to get mine going again, but they're supposed to be nice little amps.

I would definitely replace the electrolytics, I think I'm going to leave the old one in place for looks and just put some radial leaded ones underneath.

I'm replacing all 4 6BQ5s too, they all go to a common cathode resistor, so it would be a good idea to have them match as close as possible.

I'm going to replace the cathode resistor too, either with two 200ohms 4W in parallel or one 200ohm to each output pair(which will require changing the hum circuit)

I believe the on/off switch leads are the ones going to the 2 lugs closest to the center of the chassis on the lug strip with the big disc cap. One lug should have a lead from the transformer and the other a lead from the power cord, and each will have a lead going to the Tuner Power connector.
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Old 18th March 2007, 07:02 PM   #17
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Thanks Radtech.

I think they are the same amp. I connected a CD player to console preamp\tuner and listened for a while. Sounded pretty good but had slight hum. I wired in a switch and my Hafler preamp. I think the Hafler doesnít have as much gain as the Magnavox preamp but the hum is gone. The one tube isnít burnt but has carbon buildup that makes in hard to see the glow. I like your idea on replacing the big cap. Guess Iíll start looking for parts and building a wood enclosure. Thanks again.
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Old 18th March 2007, 10:12 PM   #18
radtech is offline radtech  United States
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Cool, good luck with it.
I suppose if you wanted a bit more gain you could add a dual triode tube in that extra hole in the chassis and make an extra gain stage on each channel.
There's also a hole for another pot similar to the hum balance one, that was originally for a balance control on some models.

The speaker terminals are an interesting problem. I'd like to change then from the stock spade lug, but I'm not sure what to use that won't look 'kludgey', I saw one where they replaced it with banana jacks and it just didn't look good.
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Old 4th July 2007, 06:59 PM   #19
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I finished my Maggie and caught the tube bug (see picture). I just found a model 8601 referred to in this thread. Does anyone have a schematic?

I purchased the console that included this amp for $10. The console consists of 2 cabinets; one with amp, tuner, & phono and the other just speaker and record storage. When I got it both speakers where attached to one speaker output the OPT on the channel with no speaker connection was bad.

The transformers in the picture were salvaged from a Silverstone integrated tube amp that also used 2 EL84s. I tested the 8601 with these OPTs and one channel sounds good but the other is weak. Probably why someone connected all speakers to one channel.

I plan to take this completely apart and replace everything except the transformer. Do you think these old output transformers will be ok and if not any suggestions for new replacements? Thanks.

Bruce
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Old 4th July 2007, 07:00 PM   #20
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Picture of 8601.
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