Hello all,
I'm a new member of this forum, and relatively new to monitor repairs, and I'm hoping somebody can help me with an issue I have with my WG monitor above.
I also suspect the monitor is a Zenith version, as there is 2 eht leads to the anode, the VR is an STR30130 and the HOT is marked as TZ1167. Numerous other differences on the board versus the K7000 schematic are evident also.
This monitor (part of an NBA Jam cabinet) worked fine until approx 1 week ago, when the fuse blew.
Unfortunately for me, while trying to repair this machine I made some mistakes along the way - hopefully these have not done any major damage.
Firstly replaced the Fuse - blew immediately again. Then checked the HOT - it was shorted. I ordered a 2sd1398 replacement for this, but the TZ1167 original was plastic, while the 2sd had a metal tab - I did not realise that there would be an issue with ground. Thus, after powering up the 2sd1398 sent out a nice spark and is now dead again.
Also there appears to be shorting between the VR pins, and R103 (2.7R 5W) was open. I tested all other components in the power train and they seem good. While awaiting replacement parts I have tested the rectifier parts, and at this point at the output of the rectifier stage im getting 170V DC (obviously no connection to the VR or HOT and no load on the circuit).
Through the forums here I have checked a number of other parts, D18 , the safety caps across the HOT, and all other parts and they seem to be good. One thing is bothering me though, and this is in reference to both the HOT circuit and the STR VR.
With a new HOT installed I can get a continuity signal from output to ground - This I think is happening through T2, which is showing about 0.8R resistance so would be explained. But with HOTS in Ireland approx €7 a pop its an expensive business being wrong.
Similarly, with STR30130 costing approx €20, I cant afford just to drop them in and see what happens.I have now ordered a replacement STR30130, and a like replacement of the TX1167 (which is as far as ?I can recall a 2sdxxxx but not a 1398). Mica washers behind both VR and HOT will be checked from now on I can assure you.
So (after the essay), I'm wondering if 1) it is possible to run the chassis WITHOUT the VR installed (maybe with the HV shutdown D10 diisconnected to test HOT operation?
2) Can I install the VREG but leave the output pin disconnected while I try to measure the voltage output, which should be about 130V? Will this work and will it cause any damage?
3) Is the resistance in the secondary winding of T2 an issue?
4) is there a specific zenith K7181 schematic?
I've checked D18 etc and caps in the HOT/yoke section of the PCB and these look well. Ive alwo been running the monitor with the degauss disconnected.
The dag wire on the CRT board was broken - butthis happened due to the constant pulling in and out of the chassis.
I havent capped the monitor yet - but actually have most caps replaced. The line output transformer looks good - no goo etc, and was working fine until this unknown incident occurred.
Also wondering how you work safely on this chassis live - to me just discharging the anode is not enough (even though my anode is not working at the minute), but access to the board while connected to both the anode and CRT is akward to say the least.
Thanks in advance for any help you might have - I'm anxious to get this repaired.
Please forgive the essay, and I'd appreciate any advice. Especially anything I can do to save myself blowing VR's and hots. Also, hope I made sense.
Regards
Ger
I'm a new member of this forum, and relatively new to monitor repairs, and I'm hoping somebody can help me with an issue I have with my WG monitor above.
I also suspect the monitor is a Zenith version, as there is 2 eht leads to the anode, the VR is an STR30130 and the HOT is marked as TZ1167. Numerous other differences on the board versus the K7000 schematic are evident also.
This monitor (part of an NBA Jam cabinet) worked fine until approx 1 week ago, when the fuse blew.
Unfortunately for me, while trying to repair this machine I made some mistakes along the way - hopefully these have not done any major damage.
Firstly replaced the Fuse - blew immediately again. Then checked the HOT - it was shorted. I ordered a 2sd1398 replacement for this, but the TZ1167 original was plastic, while the 2sd had a metal tab - I did not realise that there would be an issue with ground. Thus, after powering up the 2sd1398 sent out a nice spark and is now dead again.
Also there appears to be shorting between the VR pins, and R103 (2.7R 5W) was open. I tested all other components in the power train and they seem good. While awaiting replacement parts I have tested the rectifier parts, and at this point at the output of the rectifier stage im getting 170V DC (obviously no connection to the VR or HOT and no load on the circuit).
Through the forums here I have checked a number of other parts, D18 , the safety caps across the HOT, and all other parts and they seem to be good. One thing is bothering me though, and this is in reference to both the HOT circuit and the STR VR.
With a new HOT installed I can get a continuity signal from output to ground - This I think is happening through T2, which is showing about 0.8R resistance so would be explained. But with HOTS in Ireland approx €7 a pop its an expensive business being wrong.
Similarly, with STR30130 costing approx €20, I cant afford just to drop them in and see what happens.I have now ordered a replacement STR30130, and a like replacement of the TX1167 (which is as far as ?I can recall a 2sdxxxx but not a 1398). Mica washers behind both VR and HOT will be checked from now on I can assure you.
So (after the essay), I'm wondering if 1) it is possible to run the chassis WITHOUT the VR installed (maybe with the HV shutdown D10 diisconnected to test HOT operation?
2) Can I install the VREG but leave the output pin disconnected while I try to measure the voltage output, which should be about 130V? Will this work and will it cause any damage?
3) Is the resistance in the secondary winding of T2 an issue?
4) is there a specific zenith K7181 schematic?
I've checked D18 etc and caps in the HOT/yoke section of the PCB and these look well. Ive alwo been running the monitor with the degauss disconnected.
The dag wire on the CRT board was broken - butthis happened due to the constant pulling in and out of the chassis.
I havent capped the monitor yet - but actually have most caps replaced. The line output transformer looks good - no goo etc, and was working fine until this unknown incident occurred.
Also wondering how you work safely on this chassis live - to me just discharging the anode is not enough (even though my anode is not working at the minute), but access to the board while connected to both the anode and CRT is akward to say the least.
Thanks in advance for any help you might have - I'm anxious to get this repaired.
Please forgive the essay, and I'd appreciate any advice. Especially anything I can do to save myself blowing VR's and hots. Also, hope I made sense.
Regards
Ger