zenith ga63adg25x Blowing fuses??

[JP1]

HI Guys,
I have a MK4 cabinet that has a zenith ga63adg25x Monitor in it. Worked when I bought it, then i trailered it home didnt work when i got home.
Now, I have replaced the caps....
BUt befor I did that the fuse had already blown.
(the 250v 2amp on the back of the chasis)
I measured across the white ceramic resitor on the lft side of the chasis (25 watt 180 ohms) but get a 0 reading but when i measure my other machines they read out at the rated resistance. I desoldered the connection to the ceramic resistor thinking it was the problem but then when I measured it "OFF" the board it was fine????

ANy help would be appreciated.
The first pic shows the resistor that i suspected
the second is just a pic of the chasis.
what can I do to check or test for this problem?

 

[Buffett]

if your resister is reading fine out of circuit and bad in circuit.
you probably have a bad VR.

use your diode test and see if you get a constant beep between any of the pins on the VR.
if you do it is shorted. take it out and verify it again.

test your H.O.T VR, C36 and diodes 19-24 they may be blown as well.
use your diode test for theses parts as well.

also cap it and replace the fly it looks like it has wite nobs on it.

that is a K7000 chassis and requires an isolation transformer.
MK4 cabs did not come with a isolation transformer so you will need to add one to run this monitor chassis.

Peace
Buffett

 

[JP1]

Thanks for the reply...
SO i tested the Vr (voltage regulator i assume) ran an Ohmeter on test accross the different leads (5 in total ) and did have 2 sets that were beeping...
WHat is the H.O.T vr ?? i cannot find the c36 (will i need to remove a lead to test the 19 -24 diodes? or can I do on in the board? ( on the board i get continuity in both directions on all 5 of them)
I already replaced all the caps but not the flyback.... how can I test it?

As far as the isolation transformer this is a 130vDC ? seperate transformer.

I looked at the k7000 manual and they also say to look at the Q11 too.. do i just test with an ohm meter as well?

I would like to save this thing if I can and I find this stuff interesting to say the least, so thank you again for all the help.....
THe other problem that i am having is sorcing the parts i tried the part numbers on the VR (IC4) and the Q11 (transistor) and get no matches. Do you have these parts for sale?

 

[Buffett]

yes the VR sounds like it is bad.

the H.O.T is Q11 on the L shaped heat sink next to the fly back. test with diode test. black lead on the center leg and red on each outside leg. the two outside legs will read a dead short that's normal but center to either leg means it is probably bad. pull and recheck.

C36 is rite behind it under the heat sink. it is usually a 4 legged cap. some times its 2 caps C35 and C36. if that were the case it/they sit rite next to each other. see if it/they are shorted using the diode test. means pull and check again.

you can test the diodes in circuit yes. but sounds like you already have and they test bad pull one leg and test them again.

the fly back you cannot test if you don't have a ring tester.
if it has wite nobs replace it any way. it is on its way out sooner than later.

yes the ISO transformer is a separate transformer you will have to add.



i have all the parts but the fly back and the iso transformer.

if you want i can sell them to you except the fly and the iso transformer.

or if you don't want to fool with it i can fix it for you.

test all the parts and report back with your findings.

Peace
Buffett

 

[JP1]

Sent You a private message.....
it doesnt look good

 

[modessitt]

If you ran it without the iso, not only would the VR and fuse blow, but also some of the diodes (D19-22) and you possibly smoked the resistor there near the filter cap...

 

[JP1]

YA, ans some of the tracing on the back of the board is NG....i had to jumper across one piece..... AND YES all those diods your talking about are all No GOOD. BLAH. (some good news the resistors are all good I may just send the board to Buffett if the repair is reasonable. I sent him a private message about the fix...I cant seem to find the VR and the Q11 HOT from my supplier.... and im not very experianced at this stuff anyhow. I only replaced all the aluminum caps and have heard that some of the others should be done too in a cap rejuve.... So....... we'll see I report back once I decide if its a new used monitor or a fix....I really would like to get this one working.
ANother question..

If I get the chasis working can I use it on a better tube? if the pins line up on the back?

 

[Buffett]

sounds like it got really hot at one point if you have burnt up traces. some K7000's do get hot that's for sure.

i have had to repair a few holes in them and replace pin headers for the yoke.

Peace
Buffett