SORRY, CHARLIE!

Lazarus Short

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#1
I finished packing up the Sumo Aurora tuner this morning, and so pulled out the Charlie for a look over. There was a bit of dirt, and I suspect the switches need cleaning, but everything looked more-or-less OK...wait - there's a oddly-angled cap in the corner that doesn't match the others - it's the only gray one in there, and it's on it's side. Yup, someone just left the old wires hanging out, and soldered the cap to them. I wonder if they got the right value in there...? Worse, the component position is labeled "D301." Dayam! That may just be the whole problem. Now to see if I can find a schematic somewhere...maybe a service manual.
 

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#2
I finished packing up the Sumo Aurora tuner this morning, and so pulled out the Charlie for a look over. There was a bit of dirt, and I suspect the switches need cleaning, but everything looked more-or-less OK...wait - there's a oddly-angled cap in the corner that doesn't match the others - it's the only gray one in there, and it's on it's side. Yup, someone just left the old wires hanging out, and soldered the cap to them. I wonder if they got the right value in there...? Worse, the component position is labeled "D301." Dayam! That may just be the whole problem. Now to see if I can find a schematic somewhere...maybe a service manual.
Looks like a diode to me :)
 

Lazarus Short

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#4
Looks like a diode to me :)
Yes, but are you speaking of the grey thing or the place it is soldered to? The gray thing looks like a cap to me - I really don't know my diodes - what kind should I ask for at an electronics part store? I found a schematic on the www, but I'm no expert at reading them.
 

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Yes, but are you speaking of the grey thing or the place it is soldered to? The gray thing looks like a cap to me - I really don't know my diodes - what kind should I ask for at an electronics part store? I found a schematic on the www, but I'm no expert at reading them.
Please post the schematic and we will help you out to determine what is needed. (I was only kidding on the cap!)
 

Lazarus Short

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#6
Please post the schematic and we will help you out to determine what is needed. (I was only kidding on the cap!)
I downloaded a schematic and found D301, but the number under it (a part number?) is very hard to read. I think it says "155130." Does that make sense?

EDIT: D301 is located toward the left-middle of page one.
 

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I downloaded a schematic and found D301, but the number under it (a part number?) is very hard to read. I think it says "155130." Does that make sense?

EDIT: D301 is located toward the left-middle of page one.
Looks like a 1N4148 or 1N914 application upon first inspection.
 

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#13
I'm late getting back to this thread, but I decided to wait until we picked the car up at the shop to go to Electronic Supply, which is in walking distance of the auto shop. The shop owner used to run a tube amp in his shop stereo. btw. Anyway, I bought the diodes (2) and they were so cheap and so small. Opened the Charlie up and managed to tip the circuit board up where I could work on it. Took off the rogue cap, to find that it had been soldered on top of the original diode - I guess I'll never know the backstory on that. Soldered in the new diode, screwed everything back together (no screws short or left over), connected an antenna, patch cords, and power. Wow! Beautiful FM! It tunes fine, pulls in stations, there is NO bleed over into adjacent channels, and the tuning presets work as they should. The FM is almost completely noise-free when tuning. Another for the list of great tuners I have owned.
 

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Lazarus Short

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#15
Way to go Laz. Good save brother. And thumbs up to detective work by Joe.
Is it a keeper?
Thank you, Mike. No, I think I'm going to sell it, as the Proton 300 gives me FM that is just as good, even though it looks like I've got a mini-microwave oven in my stereo. Barring that, it would be a keeper.

How is it going with the the Diana pre?
 
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Lazarus Short

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#16
Yes, I'd love to have a listen - those Dahlquists were very impressive. I know what you mean about nothing to listen to - we have a number of FM stations in the KC area, but little that is really worthwhile.
 
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Lazarus Short

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#17
Rats. I powered up the tuner & amp a while ago, and the right channel is out. Went to the CDP and got both channels. So the amp and speakers are OK. What could be wrong? Every FM station is having the same problem, so it must be Charlie.

EDIT: Yup, it's the RCA output block - it must have an open connection. Looks like I'll have to run wires to the output terminals, at least for the right channel.
 
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orange

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#18
I got your Aurora tuner Friday I think it was, it came as you sent, one red light for power and no display...have not hooked into the amp to see if the display is just dead or checked the internal fuses etc yet, just put her together for pictures.

MVC-005S.JPG MVC-007S.JPG

I have to tighten the knobs back up you took off (that was probably not necessary, looking at them) and I think I got the AM bar antenna connections back in correctly (sorta tricky for a blind bat like me, you don't want to hear me swear trying to put little connectors in tiny cramped spots on motherboards) but I think I got it.
 

Lazarus Short

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#19
I'm glad it arrived in good shape, and let me know if you get it working again. If working with tiny components on a motherboard gets to you, consider tube-era gear without circuit boards.
 

orange

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#20
Some of those point to point connections used bare wires and were kinda sharp.

Try changing lamps on some Sansuis (like 5050 and 7070).
 
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