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Old 5th July 2013, 10:32 PM   #1
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Default Monarch STA 100X weird?

So I have started to work on recapping the receiver that I had purchased a couple months ago and stumble upon this resistor that is not connected to anything at one end. It sticks out of the enclosed metal cage that houses most of the circuitry, as seen in the pic. I found a picture of the same amp on eBay with that same resistor arrangement. What might this be for?
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Old 5th July 2013, 11:03 PM   #2
llwhtt is offline llwhtt  United States
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It's part of the tuner, anytime you see a length of wire sticking up and going no where it's called a gimmick. It's cut to length as part of aligning the tuner,
leave it be.

Craig
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Old 5th July 2013, 11:06 PM   #3
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I see. Thanks for the info!
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Old 23rd July 2013, 07:03 PM   #4
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So I got it recapped and replaced the bulbs with LEDs. It sounds fantastic... except for on phono. Would something like this have a built in phono preamp and RIAA equilization? Or back in the 60's would that be a separate piece of equipment? Right now it is playing but sounds like there is no preamp.
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Old 24th July 2013, 12:24 AM   #5
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This thread on Audio Karma shows some pics of the receiver. It could easily be the case that the unit was designed to be used with piezoelectric, not magnetic, carts., as it looks like most of the tubes are for the tuners.

Please post clear pics of the front and rear panels. I want a good look at the source selector switch options. Also, that pot. on the rear panel interests me.

You probably have to manually trace the circuit out and draw a schematic. Obviously, the audio, not RF, area is of greatest interest. If you do that, please post the schematic. Perhaps, like some Sansui units, the receiver has a SS phono section. However, given your description of almost complete inaudability, I would not get my hopes up.
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Old 24th July 2013, 01:28 AM   #6
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I may have one of these - at least, I know it's a Monarch. I believe it has SE 6BM8 outputs, though I might be getting it mixed up with another old receiver.

Edit - I just searched the forums, and I have the same receiver - it has SE 6BQ5 outputs, ripe for some sort of partial feedback setup with a pentode front end.

Last edited by wrenchone; 24th July 2013 at 01:32 AM.
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Old 24th July 2013, 02:06 AM   #7
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Quote:
I just searched the forums, and I have the same receiver - it has SE 6BQ5 outputs, ripe for some sort of partial feedback setup with a pentode front end.
IIRC, the A/K thread mentioned 7189s, 6BQ5s on steroids.

Do you have a schematic?

The "iron" didn't look crappy and, I believe, there's a choke too. How about a mix of short loop (Schade) NFB nested inside a GNFB loop of only a few dB. The "gotcha" is that single Noval tube, almost certainly a 12AX7. Perhaps hybrid cascodes, with 6922 sections "downstairs" and ZVN0545As "upstairs", would work for the small signal complement.
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Old 24th July 2013, 02:30 AM   #8
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Whatever - that receiver has sat in a pile of some other stuff for some time. It'll be a while (quite) until I get to it. Wimpy 'AX7s begone!

BTW - still no schematic, though I wouldn't be surprised if the receiver was set up for ceramic phono, as it looks like a budget deal. The actual tubes in the sockets were 6BQ5s, though they might get replaced with 6P14P-EV, since that's what I've got on hand.

Last edited by wrenchone; 24th July 2013 at 02:38 AM.
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Old 24th July 2013, 01:41 PM   #9
TheGimp is offline TheGimp  United States
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I've got the STA400X, and it has two phono inputs, ceramic and magnetic. If you only have one input, it is more likely ceramic. If so, you could change it to magnetic input.
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Old 24th July 2013, 02:28 PM   #10
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Here are some pics of the top side of the amp and the front panel and rear.
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File Type: jpg IMG_1032[1].jpg (906.5 KB, 26 views)
File Type: jpg IMG_1033[1].jpg (706.8 KB, 20 views)
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