Tandberg disaster (Tandburnt!!) - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

ben · 20th Feb 2012, 1:04 am

You need to do the checks mentioned in posts 55, 56. Get at the solenoid, desolder one leg of the diode across it, and measure its resistance. Then do the same for the coil. Post back with findings.

scottie_UK · 20th Feb 2012, 8:59 pm

Quote:

Originally Posted by ben

You need to do the checks mentioned in posts 55, 56. Get at the solenoid, desolder one leg of the diode across it, and measure its resistance. Then do the same for the coil. Post back with findings.

Im confused now as Michael said in post 59, that after re-checking the board diagram he inferred that if failing D503 or D504 would blue the fuse whether or not the solenoid was plugged in.

Also which leg am I removing and on which diode? D503 or D504?

ricard · 21st Feb 2012, 6:59 am

I think Michael was assuming that the diodes would be mounted on the solenoid itself, which they are not. So if you unplug the solenoid and measure the coil resistances that'll be what we're looking for.

I know you've done similar or identical measurements before, but the results were slightly confusing. Perhaps it would also help if you did measurements both on the transfer wheel solenoid as well as on one of the others, just so we can correlate the measurements done on a supposedly good solenoid with measurements done on a supposedly faulty one.

I'm not sure the resistances are equal among all three solenoids though (would have to check the service manual), but it would give some indication if there is anything odd with the actual measurements.

(Technically, it makes sense to mount the diodes near the coils themselves to avoid long stretches of wire along which the current flows which the snubber diodes are handling, which is why one might initially assume that it has been done that way.)

20th Feb 2012, 1:04 am	#61
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Tandberg disaster (Tandburnt!!) You need to do the checks mentioned in posts 55, 56. Get at the solenoid, desolder one leg of the diode across it, and measure its resistance. Then do the same for the coil. Post back with findings. __________________ Regards, Ben.

21st Feb 2012, 6:59 am	#63
ricard Octode Join Date: Mar 2006 Location: Lund, Sweden Posts: 1,632	Re: Tandberg disaster (Tandburnt!!) I think Michael was assuming that the diodes would be mounted on the solenoid itself, which they are not. So if you unplug the solenoid and measure the coil resistances that'll be what we're looking for. I know you've done similar or identical measurements before, but the results were slightly confusing. Perhaps it would also help if you did measurements both on the transfer wheel solenoid as well as on one of the others, just so we can correlate the measurements done on a supposedly good solenoid with measurements done on a supposedly faulty one. I'm not sure the resistances are equal among all three solenoids though (would have to check the service manual), but it would give some indication if there is anything odd with the actual measurements. (Technically, it makes sense to mount the diodes near the coils themselves to avoid long stretches of wire along which the current flows which the snubber diodes are handling, which is why one might initially assume that it has been done that way.)