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sq225917
02-09-2011, 13:18
Can anyone with a 640p answer a simple question for me. Can you hear a relay click momentarily after you switch it on? I have one in for repair and think I have narrowed the fault down to the small signal relay.

cheers.
colinB
02-09-2011, 13:21
I used to have one running through a rotel amp. The rotel had a very audible relay click but i cant remember hearing anything from the 640.
Tarzan
02-09-2011, 18:13
No, no click here either.
sq225917
03-09-2011, 17:07
Dodgy capacitor replaced, yup the relay clicks audibly if you are sat close enough.
Hypnotoad
06-09-2011, 02:16
It takes around 20 seconds for the relay to click in on these.

The biggest problem is that people connect DC power packs to them and it burns out C6 from memory.
sq225917
07-09-2011, 22:48
Hypno, exactly what this guy had done, first cap on the positive leg of the PSU. So I swapped it out, and the same cap in the - rail for a 470uf panasonic FC. Replaced the main caps on the gain stage with 2200uf FC's, replaced some of the small signal caps with styrenes. Replaced the ceramic disks decoupling the opamp buffer in the gain stage with silver micas and then added a tiny little Blackgate Hi-Q nx 0.1uf directly between pins 4-8 on the underside of the opamp beneath the pcb.

Stuck it back in the post Special Delivery, which was a tenner, and only charge him £15 total. That's my good deed for the week.
Hypnotoad
14-09-2011, 02:03
Hypno, exactly what this guy had done, first cap on the positive leg of the PSU. So I swapped it out, and the same cap in the - rail for a 470uf panasonic FC. Replaced the main caps on the gain stage with 2200uf FC's, replaced some of the small signal caps with styrenes. Replaced the ceramic disks decoupling the opamp buffer in the gain stage with silver micas and then added a tiny little Blackgate Hi-Q nx 0.1uf directly between pins 4-8 on the underside of the opamp beneath the pcb.

Stuck it back in the post Special Delivery, which was a tenner, and only charge him £15 total. That's my good deed for the week.

Panasonic FC's are one of my favorite caps, cheap, good quality and sound pretty good. I have upgraded over a dozen of these and it takes them to a new level. AD823 / LM4562 op amps are a good combo.;)