Main > Monitor/Video Forum
Pentranic 1132 (CH-288) No Picture & Chirping - [FIXED!!!!!!]
grantspain:
the pentranic use phillips bu2520,
beware with these as I and a few other techs have had serious problems with all phillips deflection transistors recently
i tend to cross reference to a toshiba transistor like 2sc5422
Rickn:
Go to my website... www.niemandisplays.com download from CRT based products the CGA/standard schematic. Next measure the HOT collector to ground (Q401- BU 2520).
A great trick. desolder and remove the HOT (Q401).... now connect a 60 watt bulb from collector to ground. If the bulb lights as normal, check the volyage at the cathode of d501, should be somewhere between 113 and 130 volts DC depends on the tube used. If so power supply is fine.
Then the problem is likely in the horizontal circuit ... again Q401, but if not check electrolytics on that line especialy C313 and C501.
Good luck
Rick Nieman
www.niemandisplays.com
rick@niemandisplays.com
qrz:
--- Quote from: grantspain on April 28, 2008, 05:47:13 pm ---the pentranic use phillips bu2520,
beware with these as I and a few other techs have had serious problems with all phillips deflection transistors recently
i tend to cross reference to a toshiba transistor like 2sc5422
--- End quote ---
FYI, Grant. there seems to be more and more counterfeit semiconductors showing up at "bargain" part suppliers,
and china seems to be the biggest offending source - go fig ::)
so, best to know by whom and where ur replacements are mfg'd !!!!
qrz
grantspain:
i bought my last batch from farnells in the u.k,i only use major suppliers as i work for an international company so we have accounts with a few large european component suppliers
i returned the entire batch after the sixth failure and they sent some more with the same result-bu2520 and bu2727
now i don't bother with phillips and only buy toshiba,its difficult enough to diagnose a problem let alone deal with substandard components
gokun:
Ok...so I discharged the monitor, got the boards out and all ok and am in the process of checking things out now. I've started with your recommendations and checked capacitors 313 and 503 and the HOT.
The capacitors seem to be ok, but the HOT seems like it might be faulty...but I'm not sure I am testing correctly here...could someone go over the test procedure with me please so I can be sure I'm reading it right? TIA!
Assuming it is, in fact, bad, I will order a new one(the toshiba one recommended)...in the meantime I'm just going to continue checking components on the boards to be safe. On the bright side, no noticeable damage, burn marks, etc. anywhere.
So aside from verifying that I'm testing the HOT correctly, does it sound like I'm on the right track here?
Thanks again for any and all help!
[Edit]
Forgot to mention, I tried the lightbulb thing and it did light up, proper voltage, etc...so that should mean no power problems hopefully.
BTW: Rick, could you please give me a quote on a replacement crt in case I can't fix this one? Thanks!