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HackerNAP Help Needed

T

TOR

pfm Member
Hi,

I've finally got arpound to putting together my long overdue HackerNAPs and all is not well.

On initial power up there was a nasty smell coming from the bias resistors :(. On inspection I can't seem to find anything obviously wrong. So I removed the output devices and powered up again, this time there was a bit of smoke from R21 and R23??? Next step I've removed TR7 and TR8 and wafted the meter around with the following results:

https://www.dropbox.com/s/fc4akppyswj6yae/HackerNAP Schematic v1.6.png?dl=0

Any ideas what might be going on?

Cheers,

Tim
 
Had you previously powered up with out the output devices and got the correct readings or did you just go for broke?
 
You seem to have 65V on the emitter of TR5 and 54V on the collector of TR6 which are directly connected.

I would whip out TR4-6 and test/replace them but +1 on the photo.

Pete
 
The y are probably shot, but something has made them go. Are you sure all the 0v connections were solid before you powered up? This happened to me.
 
Thanks for the replies, much appreciated.

I just went all or nothing, only checked the PS3 and the board went in whole. Overly eager I know...

Pete, TR5 & TR6 doesn't look right probably just a recording error. I'll try replacing TR4-6.

I check all the 0v all test fine and are solid.

All the diodes seem to be OK, I'll check the resistors.

Sorry about the picture quite difficult to see the board in the case. The uninstalled board only was built at the same time, not ideal I know but there may be a systematic error.

https://www.dropbox.com/sh/s5g0m7wog1snsjf/AAAePRhJ8ARPkvf_Fa0K_Mfqa?dl=0


Cheers, Tim.
 
Did you power up the PSU sections on thier own to test them?
If so, did you discharge the capacitors before connecting everything up?
A fully populated HackerCap will hold its charge a fair while!
 
Tim
I can see a cap in the wrong way round in pic 3
Its the right lower electrolytic near the 10uf blue film caps C7?

Alan
 
Good spot on C7 gents, swapped it round. Fortunately I hadn't tried powering that one yet.

So I've replaced TR4-6 with new parts and re-tested the diodes. I'm still getting 56V & 54V on the bases of TR7 & TR8 respectively. Surely this isn't right? This is with the OP PSU disconnected.

Any ideas?

Tim
 
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