SX-780 Protection Relay

tjg79

tjg79

Member
I bought this "not working" receiver a year ago off eBay and just decided to take a look at it. It powered up, but without the relay click. As I was taking some voltage readings at the Darlington Power Packs, I heard the relay click. Now it's working fine. It's all original electronics.

It needs a recap, but I'm going to change the relay first. The original is a Fujitsu FRL-264 D048/04AL-01. This is my second SX-780 and this one is made in Korea. I bought my other SX-780 in 1979 and it's made in Japan.

I don't see a matching Fujitsu relay online. Does anyone know of a good replacement?

Thanks for the help.
 
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http://www.audiokarma.org/forums/in...-relay-replacement.150439/page-2#post-6759577
The Relay only does what the protection board tells it to. I'd rebuild the protection section on the main board, 1st. Sounds like you have a flaky cap/transistor that is responsible for the operation of the relay. But a new relay isn't out of the realm of things. Go with theactuating gear 1st and if it doesn't improve THEN replace the relay.

This thread for overhaul parts is originally from 2009 but parts are newer. Some of the more active guys on this forum probably have newer lists. Read and make notes from this thread and between those and the attachments, you will probably have the complete list. http://www.audiokarma.org/forums/index.php?threads/sx-780-recap-list.213265
 
If the relay clicked in while poking around at the power packs, I would check/reflow all the solder connections on those pins before going any further.
 
Using the meter on a powered module can cause the relay to (dis)engage.
But:
Check you amp settings to be sure the set is correct.
 
Well, it's not working perfectly. When I turn the volume knob to the 3 o'clock position, the protection circuit kicks in. After a few seconds, the relay will click on again and then click off while in the 3 o'clock position. It's good at the 2:30 position.

I haven't started working on this project yet.
 
By chance have you checked the dc offset before the protect kicks in? It would be good to determine if it is in fact being triggered by high dc offset or if it is erroneously going into protect due to a fault in the protect circuit.
 
creeve said:
By chance have you checked the dc offset before the protect kicks in? It would be good to determine if it is in fact being triggered by high dc offset or if it is erroneously going into protect due to a fault in the protect circuit.
Click to expand...

No, I haven't done any serious troubleshooting since my initial checkout when the protection relay started working again. As I indicated, I was just tracking the power to the DPPs when I heard the protection relay click. I've got a few higher priority projects before this one goes under the microscope. I've been reading old posts to get up to speed and making a list of all the good suggestions. I've got another SX-780 that needs a 37 year recap as well.
 
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