Wells Gardener 19V1001

[Ronnie Dent]

Right Q101 one leg is 110v other is 74.1 pot does little maybe mili volts on the 74.1v. Q102 Emitter is 74v Base is 73v pot changes these about 1 volt collector is 110v. Q204 collector and base can change from 49v to 57v with pot, 10watt resistor is getting hot during testing volts? hope I got this right? difficult to read volts and pins and change pot from top and bottom of chassis

Thanks Ronnie

 

[obcd]

Remove the HOT Q103 and see if that makes a change.

It looks like there is an overload on the B+ voltage. It might be a defective HOT or LOPT. (just a wild guess) You might not let it run to long like that as Q101 might overheat and fail again.

 

[Ronnie Dent]

Thank you, will try that tomorrow, hopefully the lopt will not be bad!

Thanks Ronnie

 

[Ronnie Dent]

Hi again, with Q103 removed B+ is around 72.7v adjust to 73v with pot that is full up and down of the pot?

Thanks Ronnie

 

[Ronnie Dent]

Hi again, with Q103 removed B+ is around 72.7v adjust to 73v with pot that is full up and down of the pot?

Thanks Ronnie

Hi obcd not sure if you are about or missed my post, if it's not an easy fix no problem as I would just keep it for a spare

Thanks Ronnie

 

[obcd]

If you disconnect one side of R106, B+ voltage should become 110V if that is not the case, the B+ voltage likely needs to provide 2 much current. Did you also replace the capacitors that represent C101 in the schematic? If not, is that capacitor heating up? Do you have a way to disconnect the B+ (75V) from all the chassis loads, only leaving your 60W light bulb as a load? That would prove if the problem is in the B+ regulating circuit or if it's indeed an overload. Besides the horizontal stage (The LOPT) there doesn't seem to be connected much to the B+ that might be able to overload it. You could remove the light bulb and see if the 75V goes up without that load. You did replace Q101 and Q102 if I remeber well?

 

[Ronnie Dent]

Hi, I have only replaced Q101 as it was short and removed the hot Q103, not sure how I could isolate the B+ from the rest of the chassis, will try remove R106 see what happens, it looks as if the large 10w resistor has been hot for a long time in it's previous use as the casing is brown around those resistors?

Thanks Ronnie

 

[obcd]

It's normal for a 10W resistor to become hot. After all, it's designed to dissipate maximum 10W. Some solder irons are only 15W. You could compare it to your working chassis. It will likely become hot there as well. I understand that disconnecting the hot can be difficult. Lowering your load again from 60W to 15W or even totally disconnecting it might be an easier option to lower the load.obcd2015-08-21 19:57:30

 

[Ronnie Dent]

Sorry for the delay have had car troubles! With the lamp removed the B+ is 100.2v I can increase to only 100.8v with pot? not located R106 yet is it still worth doing that test?

Thanks Ronnie

 

[obcd]

If I remember well, on previous chassis, the B+ voltage was higher than the expected 75V, even with the 60W load connected. On this one, it's 2 low, even with the load removed. With R106 removed, it should become higher if it's the regulating circuit that pulls the voltage low. So yes, I am afraid that test could still be usefull. Maybe you can find the resistor if you follow the pcb tracks from the connected transistors.

 

[Ronnie Dent]

Thank you, I tracked down R106 from collector of Q204 it is mounted in the chassis not on the pcb, lots of parts are fly wired off the pcb so not marked, so I snipped one leg R106 and I have 114v?
Also hot and lamp still removed
Ronnie Dent2015-08-24 20:48:18

 

[obcd]

Can you check the emitter voltage of Q204 with the adjustment in both directions? It should be a stable voltage of 30 - 33V It's base voltage should be 0.7V higher and remain like that as well.

I am suspecting Q204 or ZD 201.

 

[Ronnie Dent]

The emitter of Q204 reads 31v slowly rising started at 30.67v and the base reads 41v also slowly rising with no load or hot fitted, across ZD201 I get 31v.

Thanks Ronnie

 

[obcd]

Q204 is defective. It's base voltage should be equel to it's emitter voltage (0.7V higher) to be exactly.

 

[Ronnie Dent]

Q204 is defective. It's base voltage should be equel to it's emitter voltage (0.7V higher) to be exactly.

Great thanks, that was bad in the other chassis too but not in the same way. I have some so will swap it out

Thanks Ronnie

 

[Ronnie Dent]

I replaced Q204 it's much better but not sure it's right yet? B+ is adjustable from 71v to 87v with 60w lamp

Thanks Ronnie

 

[obcd]

Maybe it's time to connect the hot again and try the chassis connected to the tube. Don't forget to remove the link that disables the horizontal stage (if that's still there). It's adjustable and the 75V you need is within the adjustable range, so it's worth a try.

 

[Ronnie Dent]

Okay thanks will give it a go and report back

 

[Ronnie Dent]

Sorry for the delay but only had time today to try the chassis in the machine, I'm happy to report this chassis is fully working! on connecting I had a B+ of 87v screwed it down to 75v and it's producing a nice bright picture despite still having the old capacitors, this gives me a working spare and hopefully I will soon have 2 working boards too.

Thank you very much for guiding me through fixing both of these chassis, it's clear you know your stuff.

Thanks Ronnie

 

[obcd]

Accurate feedback is important as well.

Good to hear all are working now.