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Bose 1800 series 1 restoration - help appreciated!

Were these measured "in circuit " ? Should have all measures in the high megohms or "open" out of circuit.
 
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Yes, in circuit. Cant imagine they are all broken so as they gave about the same value i imagined they are ok.

I'm still not clear how the boards can be the culprit if r7 burns down without the boards connected?
 
belgiansound said:
es, in circuit. Cant imagine they are all broken so as they gave about the same value i imagined they are ok.
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You imagine wrong. The outputs are all in parallel. If one is 10-30K Ω then all the rest will show the same value.
 
Tomorrow i will swap the boards in my other bose 1800 amp to make sure they are ok.

I also tested now with the rectifier bridge connected and no boards, no relay, high temperature indicator is on and r7 is fine.
 
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belgiansound said:
I'm still not clear how the boards can be the culprit if r7 burns down without the boards connected?
Click to expand...
Going to depend on where the relay is picking up the coil voltage. Before the molex connectors or after the molex connectors.
 
belgiansound said:
I'm still not clear how the boards can be the culprit if r7 burns down without the boards connected?
Click to expand...
belgiansound said:
I tried again with the original rectifier bridge and without any channel connected, but with both bridges connected, now i get the high temperature indicator which goes 'on'. I guess this is because the channels are not connected.

R7 runs nice and cool,
Click to expand...

Which is it ?
 
Also make sure fuse F1 is still serviceable.If its "open" it could give you a false "over temp "indication.
 
belgiansound said:
Tomorrow i will swap the boards in my other bose 1800 amp to make sure they are ok.

I also tested now with the rectifier bridge connected and no boards, no relay, high temperature indicator is on and r7 is fine.
Click to expand...
Were you able to resolve the issue? I'm having a similar problem.
 
I completely stalled the project, new relationship, moving twice and renovating my house and 2 newborns got in the way, it's stored in the attic with a lot of dust on it...together with my dual sub build which I do want to finish this year.

I've got another one that works, i can install the boards and see what happens, just need to find some time and the courage to risk breaking another bose.

Recentlyone of my other bose 1800 (I had 3, now 2) overheated and almost damaged my speakers. Got me a bit scared tbh and I sold that unit too cheap (50 euro). My speakers are upgraded and too expensive to risk frying

I also bought some QSC amps from the EX line and that's the reason it was less urgent. They are more power full, reliable, have a GREAT sound and are just as silent as the fans only come up when they get hot, and they have variable speed so you hardly hear them ever. In bridge mode they get totally crazy, perfect for a sub. I also bought 5 "hifi" mono blocks to power my surround setup in the living room..."i've got the power"
 
I just aquired one of these which was or appeared to be in excellent condition. It was in the bose flight case with the fans and when taken out to clean looked like new inside. I put it back together and ran it awhile for a couple of old subs for my surround sound and it seemed fine. i decided to use it for my mains which sounded great. I fell asleep with it playing and woke up with the right channel meter pegged out and jumped up and switched it off. Against my better judgement, I decided to turn the switch on again and see what would happen. Lots of sizzling, popping,arcs and smoke was what happened! I immediately unplugged it and opened it up to see a wad of resistors melted into a ball and see where they came from the power on relay which had been in series to the transformer (I think). It looks like they shortedto the top due to the Denon i sat on it to use for a pre amp. I am really hoping to be able to repair it (or have it repaired) as I used to be into hifi of that era and used to have a Soundcraftsman that was similar. I dont know what size resistor is supposed to go there, but it looks like the ones that were toasted were probably not stock. I am a novice when it comes to electronics, but would sure appreciate your help or advice with this. If not, I understand as I am such a novice. I am familiar with multimeters of course and have several Fluke meters, Triplett, Tascam, Simpson, etc and I know the basics of electronic "parts" and what they do. Anyway, thank you for your time.
 
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