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Sansui 5000

I just got my MJE15032G as my tr 804 (2sc680) replacements and the MJE15033G as the TR 805 (2A566) and am confirming this is the proper re-wire

Screenshot 2025-02-18 at 8.10.06 PM.png
 
Guido57 said:
I've no experience with industrial controls. You may indeed know more about circuits than I do, but you may be over thinking things. First work to what specs and adjustments you do have. If you find something out of spec then work backwards to locate a cause. For example, if I can't adjust the bias using the service manual/bulletin's method I look at the trim pot. If the trim pot isn't the problem on a 6013 board I remove TR803, which controls bias as things warm up, and test it out of circuit. FWIW all my bias problems on the 6013 boards have been the now 50 year old trim pots, though some lists of problem transistors includes what Sansui used for TR803. Note the time I tested TR803 I traced the problem back to an unstable connection on the trim pot.
Click to expand...
I do see what you mean, the output would only adjust to 43 volts down from 75 and the bias would only adjust down to 80 ma on the left channel (I had the left and right swapped in my mind when I was working on the unit from the rear not the front)
 
jnl1105 said:
I do see what you mean, the output would only adjust to 43 volts down from 75 and the bias would only adjust down to 80 ma on the left channel (I had the left and right swapped in my mind when I was working on the unit from the rear not the front)
Click to expand...
To be sure: looking from the rear of the unit the board on the left is the left channel, right channel towards the right. This would be corresponding to the labeling on the fuses.

Yes you had the collector swapped. Correcting that I think you have it right, but check data sheets for the original TO-66 case.
What are you using for TR803, the biasing transistor?
Do you have heat sinks for TR804 and 805?
80ma bias would make it run hot. Probably light up the DBT too. What wattage are you using for the DBT?
 
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Guido57 said:
To be sure: looking from the rear of the unit the board on the left is the left channel, right channel towards the right. This would be corresponding to the labeling on the fuses.

Yes you had the collector swapped. Correcting that I think you have it right, but check data sheets for the original TO-66 case.
What are you using for TR803, the biasing transistor?
Do you have heat sinks for TR804 and 805?
80ma bias would make it run hot. Probably light up the DBT too. What wattage are you using for the DBT?
Click to expand...
currently I am only running at .2 amps or about 25 watts power
 
How are you arriving at this .2 amp and 25 watts? Are measuring .2 amp input and multiplying by 120 V?
Unless you're putting a signal through and amplifying that you won't be drawing much power. Unfortunately I do not have an easy way to measure the draw on my unit when it is idle but once the caps are charged there isn't much to draw power, hence a DBT glows at startup then dims. If one plays music through the receiver when on a DBT the light will increase as the volume, therefore the current draw, is increased. (Not something I would recommend, unless you want to see for yourself.)
Are you using a DBT?
 
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Guido57 said:
How are you arriving at this .2 amp and 25 watts? Are measuring .2 amp input and multiplying by 120 V?
Unless you're putting a signal through and amplifying that you won't be drawing much power. Unfortunately I do not have an easy way to measure the draw on my unit when it is idle but once the caps are charged there isn't much to draw power, hence a DBT glows at startup then dims. If one plays music through the receiver when on a DBT the light will increase as the volume, therefore the current draw, is increased. (Not something I would recommend, unless you want to see for yourself.)
Are you using a DBT?
Click to expand...
the math is what I am using and I have a couple of devices that monitor wattage/ amperage on the incoming plug side, I don't have any filament bulbs only led so I can't really tell by that. And from everything I remember and have read about a dot it is just to watch what wattage is going through the circuit based on brightness of the bulb
 
Lets assume for the moment that your amperage and wattage figures are good. Thing is this has nothing to do with balancing the voltage or setting the bias. If the bias is high you will generate more heat which from your description seems to be one of your problems.
Besides indicating there is too much power going through a unit a DBT helps from frying components, it's a current limiter. FWIW one can get a DBT to glow on one of these units just by turning the trim pot too far.
As I am not familiar with the instrumentation you're using I can't be certain but if .2 amps is at the lower end of your meter's scale or precision I wouldn't bet too much on its accuracy. I feel you're putting way too much stock in the amperage coming in on the plug.
I suggest you extend your efforts to find a suitable bulb.
 
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Guido57 said:
To be sure: looking from the rear of the unit the board on the left is the left channel, right channel towards the right. This would be corresponding to the labeling on the fuses.

Yes you had the collector swapped. Correcting that I think you have it right, but check data sheets for the original TO-66 case.
What are you using for TR803, the biasing transistor?
Do you have heat sinks for TR804 and 805?
80ma bias would make it run hot. Probably light up the DBT too. What wattage are you using for the DBT?
Click to expand...
I shortened the lengths and used heat shrink on the capacitors. I used some heatsinks I had laying around. I did clean up the board some more after these pictures.

IMG_3555.JPGIMG_3556.JPG



IMG_3554.JPG
 
Don't forget to physically couple TR803 to 804. Double check for shorts on those transistors.
 
Guido57 said:
Don't forget to physically couple TR803 to 804. Double check for shorts on those transistors.
Click to expand...
how come, the tr804 and the 805 on the boards weren't originally only the tr804 and the tr803 had a physical connection, does the tr803 have n electrical connection through the housing?
 
I found a 6o watt incandescent and a 35 watt. and built a dbt... With the 35watt when I first turn it on I Get an inrush current but then it is barely lit. yet I am still getting the R189 (220 ohm) resistor going bad
 
jnl1105 said:
how come, the tr804 and the 805 on the boards weren't originally only the tr804 and the tr803 had a physical connection, does the tr803 have n electrical connection through the housing?
Click to expand...
Not an electrical connection, a THERMAL connection. As I understand it TR803 is necessary to control the bias as TR804, and the circuit in general, heats up. A transistor for this purpose is common for amplifiers, though most designs put them on the main heatsinks. This is why it is important to be sure TR803 is good.
jnl1105 said:
I found a 6o watt incandescent and a 35 watt. and built a dbt... With the 35watt when I first turn it on I Get an inrush current but then it is barely lit. yet I am still getting the R189 (220 ohm) resistor going bad
Click to expand...
Are you continually frying R189 after replacing them? If so I'm guessing they're essentially acting like a fuse and there is too much current running through them.
 
Guido57 said:
Not an electrical connection, a THERMAL connection. As I understand it TR803 is necessary to control the bias as TR804, and the circuit in general, heats up. A transistor for this purpose is common for amplifiers, though most designs put them on the main heatsinks. This is why it is important to be sure TR803 is good.

Are you continually frying R189 after replacing them? If so I'm guessing they're essentially acting like a fuse and there is too much current running through them.
Click to expand...
I think I will get some tr803 replacements
essentially yes on the r189. which is weird as the tr804 is new and good and goes tr809 which a new MJ21196g
but it seems I am only getting 45 volts to the case on the tr807 now as well as at the fuse
 
Perhaps the 35W bulb is restricting things. See what voltage you get the 60W. I loose about 8V at the power caps/fuse with a 75W. One reason I readjust after I've got the unit working and take it off the DBT.
 
When using a new plastic bodied transistor for bias it is often secured to the heatsink with epoxy. I have also used zip ties to do this and had no problems under long term use.
 
since the tr803 (2sc984) are difficult to find what are the replacements people are using since it is a thermal interface that is needed also
 
On the first page of the thread you have a picture of a reproduction board that indicates 2N5088 for TR803.
I've used KSC1845 but that was using Sanken SC4883, if I recall correctly, for TR804. I have absolutely no idea what would be better.
 
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