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Technics SU-7700
Technics SU-7700
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Old 11th April 2005, 08:14 AM   #1
rhymeswthorange is offline rhymeswthorange  United States
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Default Technics SU-7700

I just got a VERY nice, clean Technics SU-7700 on eBay. It sounds quite nice, but has one problem: the right channel is significantly louder than the left. On bass hits, the power meter for the right channel consistantly reaches higher maximums than the left. I have reversed the speakers and played every sort of music I have only to come to the same results.

I have pretty sensitive speakers (fostex fe207e's in a MLTL) and am only driving about 1 - 1.5 watts through them. Much louder is just too much in my little dorm room. Could slight differences in transistor bias, minute unmatchedness of transitors, positioning in my room, or the high sensitivity of my speakers be the culprit?


Thanks!!!
-'orange
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Old 11th April 2005, 08:19 AM   #2
analog_sa is offline analog_sa  Europe
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Quote:
Could slight differences in transistor bias, minute unmatchedness of transitors,

No. NFB takes care of this. Look at passive components, bad electrolytic coupling caps, unmatched volume pot etc
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Old 12th April 2005, 01:24 AM   #3
anatech is offline anatech  Canada
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Technics SU-7700
The cap that goes from the negative feedback to ground through a resistor is opening up. That will reduce the gain - to unity when the cap is completely open or anywhere in between for partial open.


-Chris
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Old 12th April 2005, 09:29 PM   #4
rhymeswthorange is offline rhymeswthorange  United States
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How can I hunt this cap down?
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Old 12th April 2005, 09:45 PM   #5
anatech is offline anatech  Canada
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C211 & C212 should be 47 uF. C201 & C202 are 1 uF, check those too.

-Chris
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Old 13th April 2005, 09:50 AM   #6
rhymeswthorange is offline rhymeswthorange  United States
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do you have the schematic to my amp?
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Old 13th April 2005, 09:50 AM   #7
rhymeswthorange is offline rhymeswthorange  United States
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C211 & C212 are 33uf
C201 & C202 are 1uf
C266 & C265 are 47uf
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Old 13th April 2005, 09:50 AM   #8
rhymeswthorange is offline rhymeswthorange  United States
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By "check" you mean replace and see?
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Old 13th April 2005, 06:46 PM   #9
kamskoma is offline kamskoma
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Default SU-3500

Hi,

It seems that this is the right place to find people with a Technics SU-3500 schematics I need it very badly.

Thanks

The Kamskoma
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Old 14th April 2005, 12:43 AM   #10
anatech is offline anatech  Canada
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Hi rhymeswthorange,
Gottum service manual, but no scanner. I'll try to help best I can. For the cost, just replace the caps and see what comes out.

Hi kamskoma,
Don't know about yours, can't seem to find it. Sorry.
-Chris
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