Betapack ch 1&2 fault

[handyandi]

Have a Betapack 2 that exhibits the fault as described in the wiki here, & have the transistors & diodes required to change - although on opening zero 88 have not labelled board in fashion as I would expect Q5 R1,2, D1,2 etc only the component descriptions. Does anyone have the physical location of diodes D1 & D2 and transistors Q4 & Q5. The transistors around the low voltage Tx are not both BC548's which would be the ones to replace with 2N3904's. One is a ZTX450 which has a much higher collector current.

Any help before speaking to Z88 would be appreciated.

 

Andi

[Just Some Bloke]

Your best bet is to call Keith at Z88. He's great and will talk you through everything.

[handyandi]

Great thanks

[ianknight]

Unfortunately, the wiki fault relates ONLY to channels 3 to 6. Channel 1&2 derive their ramp and sync a different way and so are not susceptible to the fault.

 

First port of call should be to check the Triacs - try swapping one from channel 3 to 1 to see if that cures it (then order some spares). I don't think a channel opto failing would cause this from memory (it's usually a triac) - if swapping triacs doesn't cure the channel stuck on then get a Zero Repair centre to have a look at it as the remaining possible fault can be a cow to find.

[PaulDF]

If it is similar in design to the betapack 1 then the sync for channel 1 and 2 are derived from the transformer used to power the circuit board board via Diode D1 and D2 which are as you look at the transformer to the bottom right hand side, directly to the right of these there is a capacitor, to the right of this cap are some resistors then to the right of the resistors are transistors Q4 and Q5.

 

I'd expect a triac or an opto problem to start with one channel, not affect a pair immediately. A faulty pair of channels does smell of something to do with their sync. It is pretty streight forwards to swop the triac board between channels to check them out.

If you call/email keith he might send you the service manual with a plan of the PCB with component locations on.

 

A concurrent post has been automatically merged from this point on.

 

 

The top item in the wiki was on about channels 1 and 2 but the title said ch 3&4 or ch 5&6, I have changed the title to read channels 1 and 2.

[ianknight]

It's not easy to swap the triac boards on a Beta 2 - they don't have them, the Triac's are chassis mounted and connect to the main PCB unlike the Beta 1, it is however possible to swap the connections from the PCB but be careful when doing this.

 

Like I said - to fault find this is going to be a cow...