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Old 18th October 2005, 04:36 AM   #1
gwyz is offline gwyz  United States
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Default Need help with Sansui 5000

I have a gorgeous Sansui 5000. It is a 5000 in a black case, (it is not an 5000A nor a 5000X). I have one problem, and only one problem (everything else works 100% perfectly). When used in FM or FM Stereo there is no volume. If I turn the Level Adjust all the way clockwise and turn the volume all the way up, I can just barely here the sound. The Tuner appears to be working fine and I am getting level 5+ signals via an Audio FM Antenna. I am hoping the problem is something both common and obvious to someone because I am very good with a soldering iron. My weakness is an inability to read schematics well (other than knowing what a component is when I see it), and I have no diagnostic equipment. I have the service manual, so if someone was to tell me that it needs a new "xyz" transistor, (or resistor, capacitor, etc) on the "123" board, I could do the repair. Please help! (Thanks in advance).
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Old 18th October 2005, 12:54 PM   #2
anatech is offline anatech  Canada
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Hi gwyz,

Two simple things to check. The tape monitor switch (out) and the main in / pre out jumpers (if equipped) on the back panel.

-Chris
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Old 18th October 2005, 03:33 PM   #3
gwyz is offline gwyz  United States
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Quote:
Originally posted by anatech
Hi gwyz,

Two simple things to check. The tape monitor switch (out) and the main in / pre out jumpers (if equipped) on the back panel.

-Chris
-----------------------------------------------

Hi Chris,

Thank you for the reply. Unfortunately, it's not something simple like that. But to answer the question: First, it does not have jumper blocks. Second, when the Tape Monitor switch is in the IN position, the AM also does not work.

What I find curious is that the Level Adjust in the back had already been turned all the way up, suggesting that someone else had already tried and given up. This is an ebay purchase. This morning I wrote to the seller, who has very positive feedback and guaranteed the unit. I'd rather fix it because I paid $49 for it, and the shipping expense makes it hardly worth returning. The reason I need to fix it myself is because I live on the East Coast where the shop rates make professional repair too expensive an option.

If I just knew which part was bad I really could fix it myself.

Do you have any other suggestions? I *really* appreciated the time you took to reply. Thank you *very* much.

Sincerely,
Gregg
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Old 18th October 2005, 03:42 PM   #4
anatech is offline anatech  Canada
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Hi Gregg,
One common failure I've seen is the MPX IC failing. This may or may not be true in your case. The composite FM audio signal goes into this chip and comes out as a stereo signal. I have also seen the small filter film caps on the output short. It would be unusual to find both shorted, but I did once.

Normally I would troubleshoot this with an oscilloscope. Can you post the schematic of the MPX section, or email it to me? If you know someone with a 'scope or have access to one, let me know.

-Chris
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Old 18th October 2005, 07:57 PM   #5
gwyz is offline gwyz  United States
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Quote:
Originally posted by anatech
Hi Gregg,
One common failure I've seen is the MPX IC failing. This may or may not be true in your case. The composite FM audio signal goes into this chip and comes out as a stereo signal. I have also seen the small filter film caps on the output short. It would be unusual to find both shorted, but I did once.

Normally I would troubleshoot this with an oscilloscope. Can you post the schematic of the MPX section, or email it to me? If you know someone with a 'scope or have access to one, let me know.

-Chris
---------------------------------------
Hi Chris,

I can't thank you enough for trying to help. Unfortunately, I do not have a scanner. I do have the schematic right in front of me. The MPX circuit is showing the following parts that have to do with amplification. (Note that where I put parenthesis it means there is a "small" number to the low right of the preceeding letter):
----------------------
From the Antenna it goes to the (TUNER?) "FM PACK" (board F-1011). The first amp is identified as a High Frequency Amp and the circuit is as follows :

High Frequency Amp = FET101 = (Parts list does not list this part)
High Frequency Amp = TR101 = (Parts list does not list this part)
Mixer = TR102 = (Parts list does not list this part)
Oscillator = TR103 = (Parts list does not list this part)
END "FM PACK"
-----------------------
BEGIN first section of F-1006 board (identified on schematic as F-1005)

IC201 = TC201 = uA703E
IC202 = TC202 = MA703E
IC203 = TC203 = MA703E
IC204 = TC204 = MA703E
END F-1005
------------------------
BEGIN MULTIPLEX STEREO - (Second section of F-1006 board)
"Composite Signal Amp"
TR401 = 19KHz Amp = 2SC536V(1)E(2) = Si N-P-N
TR402 = 19KHz AMP = 2SC536V(1)E(2) = Si N-P-N
TR403 = 38KHz Amp = 2SC536V(1)E(2) = Si N-P-N
TR404 = (not identified) = 2SC536V(1)G(2) = Si N-P-N
TR405 = 19KHz Amp = 2SC536V(1)E(2) = Si N-P-N
TR406, 7, 8 & 9 are all "DC Amp" and appear to control the signal gauges which are working fine.
END MULTIPLEX STEREO - (Begin Switch Control circuit)
----------------------------

I hope this info was of some help. I read at another site someone posted a comment that all parts for the Sansui 5000 are available *except* the IC chips.

I do not have an oscilloscope, nor do I know anyone.

Sincerely,
Gregg
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Old 18th October 2005, 09:04 PM   #6
anatech is offline anatech  Canada
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Hi Gregg,
At this point, you really need to be able to trace the signal to find the fault. I will guess at the MPX section as it could kill both channels. Do you get a stereo beacon when tuned to a strong station?

I sent you a portion of a schematic to compare to your manual, just the MPX portion. My feeling is that you need some assistance from someone with some test equipment. Let me know the answer to the beacon question at least.

-Chris
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Old 18th October 2005, 09:11 PM   #7
Netlist is offline Netlist  Belgium
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Default Re: Need help with Sansui 5000

Quote:
Originally posted by gwyz
If I turn the Level Adjust all the way clockwise and turn the volume all the way up, I can just barely here the sound.
This makes me think the whole tuner section is ok and the problem might be somewhere in a setting of the knobs on the front. Perhaps this is just too obvious to be true.

/Hugo
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Old 19th October 2005, 06:26 AM   #8
gwyz is offline gwyz  United States
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Default Re: Re: Need help with Sansui 5000

Quote:
Originally posted by Netlist

This makes me think the whole tuner section is ok and the problem might be somewhere in a setting of the knobs on the front. Perhaps this is just too obvious to be true.

/Hugo
---------------------------------------
Hi Hugo,

Unfortunately, the "obvious" type problems would also be happening when in AM mode. The problem is only FM (and FM Stereo). However, I *have* tried pressing every button and combinations of buttons such as Tape Monitor, Stereo Only, Mute, etc... The knobs and buttons confuse my wife, but not me. I grew up with this equipment. I can literally set this thing up with my eyes closed.

Thanks for the offer though. I *do* appreciate every suggestion I get from anyone who takes the time to offer it.

Thank you.

Sincerely,
Gregg
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Old 19th October 2005, 06:26 AM   #9
gwyz is offline gwyz  United States
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Quote:
Originally posted by anatech
Hi Gregg,
At this point, you really need to be able to trace the signal to find the fault. I will guess at the MPX section as it could kill both channels. Do you get a stereo beacon when tuned to a strong station?

I sent you a portion of a schematic to compare to your manual, just the MPX portion. My feeling is that you need some assistance from someone with some test equipment. Let me know the answer to the beacon question at least.

-Chris
-----------------------------------
Hi Chris,

I sent you a reply via email. Yes, the schematic you sent is the correct one.

By the way, I do have simple test equipment like a voltmeter; (I built it myself from a Heathkit I bought in 1975). I also have a transistor tester, but you need to plug the transistor in. The thing actually *fixed* a transistor once. It must have been stuck somehow. It didn't work the first time I tested it, but it did the second time I tested it. Then after that it worked when I put it back in the power supply I had pulled it from.

The tester also tests FETs, Diodes, SCRs, and LEDs. However, I've only used it to test transistors.

So, what's next?

Thanks *MUCH*.

Sincerely,
Gregg
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Old 19th October 2005, 06:43 AM   #10
Netlist is offline Netlist  Belgium
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Well, the buttons are out of the game then.
Could you or Chris hand me a copy of that schematic?
I'm getting curious.

/Hugo
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