Zilphy
New Member
Hello!
I'm a novice at vintage audio repair and in my journey on becoming better at this skill, I took on a Sansui RA-700 as my first restore project.
I've replaced all capacitors, transistors and diodes on the F-1232 board. The unit passes a dim bulb test.
After merging the piece into my stack to test operation, I'm running into an issue that's making me scratch my head. Conditions and results below.
[Signal Route]
MCS 3253 TAPE 1 REC → Technics SH-8025 LINE IN → Technics SH-8025 LINE OUT → Sansui RA-700 REVERBERATION AMPLIFIER SECTION IN → Sansui RA-700 REVERBERATION AMPLIFIER SECTION OUT → MCS 3253 TAPE 1 PLAY
[Monitoring]
MCS 3253 is monitoring TAPE 1
[Result]
Pressing on front panel of Sansui RA-700 reverberation to ON or RECORD immediately cuts audio. This is also true while the unit is completely powered off and not receiving line voltage. If I crank the attenuator on the receiver, buzzing will come from both channels and I can very faintly hear the music.
I've tried the following:
- Taken the EQ out of the signal route.
- Measured AC voltage with multimeter coming from Main OUT (L & R Channels) on RA-700; AC fluctuated between 0.10 & 1.15v
- With reverb ON, switching to monitoring SOURCE restores clean audio through both channels.
- Sprayed DEOXIT on mechanical switches on Mode Selector Circuit Board (F-1263-6) and presses in/out to try and clean.
I'm going to do another look on the F-1232 board for any issues I may have glanced over.
Would anyone have any tips on where to start with diagnosis on this issue? Thank you very much for your time!
I'm a novice at vintage audio repair and in my journey on becoming better at this skill, I took on a Sansui RA-700 as my first restore project.
I've replaced all capacitors, transistors and diodes on the F-1232 board. The unit passes a dim bulb test.
After merging the piece into my stack to test operation, I'm running into an issue that's making me scratch my head. Conditions and results below.
[Signal Route]
MCS 3253 TAPE 1 REC → Technics SH-8025 LINE IN → Technics SH-8025 LINE OUT → Sansui RA-700 REVERBERATION AMPLIFIER SECTION IN → Sansui RA-700 REVERBERATION AMPLIFIER SECTION OUT → MCS 3253 TAPE 1 PLAY
[Monitoring]
MCS 3253 is monitoring TAPE 1
[Result]
Pressing on front panel of Sansui RA-700 reverberation to ON or RECORD immediately cuts audio. This is also true while the unit is completely powered off and not receiving line voltage. If I crank the attenuator on the receiver, buzzing will come from both channels and I can very faintly hear the music.
I've tried the following:
- Taken the EQ out of the signal route.
- Measured AC voltage with multimeter coming from Main OUT (L & R Channels) on RA-700; AC fluctuated between 0.10 & 1.15v
- With reverb ON, switching to monitoring SOURCE restores clean audio through both channels.
- Sprayed DEOXIT on mechanical switches on Mode Selector Circuit Board (F-1263-6) and presses in/out to try and clean.
I'm going to do another look on the F-1232 board for any issues I may have glanced over.
Would anyone have any tips on where to start with diagnosis on this issue? Thank you very much for your time!
