betapack 1 channel fault

[capristeve]

hi all, hoping you can help

have two aging beta 1s, they get fairly light use in the school where I work,

2 consecutive channels are constantly on, I bought some triacs and fitted to the relevant channels

but did not solve the problem

 

the triacs I removed are T2513MK, and the ones I fitted in their place are BTA25600B

 

so my questions are

 

have I fitted the right triacs? and could I have wired them incorrectly?

could there be another fault?

 

any help with this will be greatly appreciated

 

steve

 

 

 

 

 

[kgallen]

Did both channels fail at the same time before you replaced the triacs? If so, maybe a sync circuit problem rather than triacs? I'd take a look at the infamous 100k sync circuit resistors.

 

http://www.blue-room.org.uk/wiki/Betapack_Servicing

 

http://zero88.com/forum/topic/3709-betapack-1/#entry27190

 

Kevin

[capristeve]

yes! both channels went together (3&4) how involved is this job? swapping the triacs was easy, im assuming some solder may be involved?

[kgallen]

If you can solder, swapping the resistors is pretty straightforward. You have to remove all of the screws holding the PCB into the chassis to get to the solder side. I've done 4 Betapacks (1's and 2's) and I don't recall them being hard - the Betapack 1s I think were a bit easier as there is more room.

 

Just make sure you get the correct VR rated components as per my link. Don't just buy any old 100k 1W resistors as they are across mains voltage.

 

If you've got an ohmmeter, you can get an idea if there is a problem with the resistors - there are 4 in there so you can compare readings - but don't expect to measure 100k when they are in-circuit. Replace all of the 100k resistors not just the ones you think have failed. It'll cost you a couple of pounds to buy the correct resistors.

 

Kevin

 

ps Where are you in the UK?

[capristeve]

thanks for the info, im based in Dorset, i'll have a chat with our tech department and see if its something they can handle

[kgallen]

Ok, can't offer to fix it for you as you're not local to me. If your Tech department can't fix this then get a better Tech department because if the resistors are the fault then it's a straightforward fix!

 

Kevin

[capristeve]

ive opened up the pack and one of the resistors in reading different to the other three!

reckon I can handle this, thanks for the advice,

 

given that this is the first problem ive ever had with this kit,

its testament to zero 88 build quality!

[iank99]

Don't swap just one resistor!

 

Really.... Don't...

 

Do all four resistors because otherwise you'll be opening the pack again and removing the PCB to swap another one within 6 months - guaranteed!