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neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
Reviews:
·Bright House
reply to Mdoc

Re: Tektronix 485 - no power up

Once you said U1910, I found it.... must be blind... LOL

From ground to the BAL point, I get 60-350mv, and it bounces around....

I get 160V at the shell of Q1834, and between -70 and -140v at the shell of Q1844

So it sounds like T1960 might be bad.....
--
"F is for Fire that burns down the whole town...
U is for Uranium...... Bombs...
N is for NO SURVIVORS!!!!!" Sheldon Plankton


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
said by neonhomer:

Once you said U1910, I found it.... must be blind... LOL

From ground to the BAL point, I get 60-350mv, and it bounces around....

It's supposed to "bounce around" if you're using a DMM. The proper way to measure is not with a DMM but with a working scope with external trigger on TP1926. For the first 4 entries in table 4-4, do what you can with a DMM. See what you can do to borrow a working scope.

The voltages at Q1834/Q1844 may be from attempts to start the inverter, so it's meaningless at this point. The voltages are supposed to be double the 115v AC input voltage, or the p-p value of the line voltage. Read "Line Input Circuit" pg 3-6 2nd paragraph.

And I doubt T1960 is bad; we can't say it's bad if the problem points to circuits before T1960. It is working (in a manner of speaking) because the secondary voltages are showing the continuous inverter startup attempts made by the startup circuit. Something is preventing this, and the best method to find this out is by monitoring TP1951 with a working scope.


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1

1 edit
And if you can't get a working scope, the best way then is to look at all the inputs to the balance node indicated in the block diagram on pg 3-11 and look for shorts or opens in circuits leading up to those inputs. Look for scorch marks, too. (Cold solder joints is a possibility, too--push/pull on points on the board with a pencil or plastic probe.)


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
Reviews:
·Bright House
All I have is a Fluke 789 Process Calibrator, and a Fluke 11 DMM.

I don't know anyone with a working scope. That was the reason I bought one, so I could have one.

I will hae to fight with it more tomorrow. I wish I knew someone locally (Daytona Beach, FL area) who could assist me in fixing this thing. Its either that or I keep searching for a working scope....
--
"F is for Fire that burns down the whole town...
U is for Uranium...... Bombs...
N is for NO SURVIVORS!!!!!" Sheldon Plankton


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
Yes, try that.


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
You mean unplug the high voltage lead, or all the wiring to the CRT?


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
all wiring to the CRT (leave the HV in)


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
Reviews:
·Bright House
Oi vey.. that's going to be a bitch.......

I had the power inverter board and the sweep board out last night, and it was a bitch to get apart.

It says I can pull certain combs to isolate certain areas. I do know if I pull the "R" comb, the "clicking" goes from slow to fast.
--
"F is for Fire that burns down the whole town...
U is for Uranium...... Bombs...
N is for NO SURVIVORS!!!!!" Sheldon Plankton


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
I'll look it up. How fast is fast?


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
reply to neonhomer
said by neonhomer:

Oi vey.. that's going to be a bitch.......

I had the power inverter board and the sweep board out last night, and it was a bitch to get apart.

It says I can pull certain combs to isolate certain areas. I do know if I pull the "R" comb, the "clicking" goes from slow to fast.

The faster clicking is caused by pulling the "R" comb, Table 4-4, pg 4-8, top entry. Nothing new there.

If I'm not mistaken there should be a plug with wires attached to it on the rear of the CRT; you just pull that off.



neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
You pull the rear cover, and there are three connectors..... one has 3 wires, and two that have one wire each....


Mdoc
Ehh... munch munch... what's up, Doc?
Premium
join:2007-03-27
Sterling, VA
kudos:1
Pull them all off. The big HV lead goes to the tube anode, you can leave that in.


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
Haven't forgotten. Just don't feel like opening this thing back up right now. Will probably open back up after the kids go to bed in about 45 min or so.


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
Reviews:
·Bright House
Oooookay... Pulled the three connectors that go from the xfmr board to the crt. Nothing. Same thing.

Walked through some of the tests on 4-7. Nothing to note.

I think I have reached the limit of my equipment. I hate to have to send this to a shop, as I know it will be a few hundred $$$ to get it fixed.
--
"F is for Fire that burns down the whole town...
U is for Uranium...... Bombs...
N is for NO SURVIVORS!!!!!" Sheldon Plankton


drjim
Premium,MVM
join:2000-06-13
Long Beach, CA
kudos:3
Try and find a local ham radio club. Most of the old guys there (like me!) probably have an oscilloscope, and might be willing to help you track down the problem.
--
One man's Magic is another man's Engineering.


cowboyro
Premium
join:2000-10-11
Shelton, CT
reply to neonhomer
said by neonhomer:

I think I have reached the limit of my equipment. I hate to have to send this to a shop, as I know it will be a few hundred $$$ to get it fixed.

Yeah you can hunt a working unit if you are patient. I have a 2232 that I got for $100 *shipped*.


neonhomer
KK4BFN
Premium
join:2004-01-27
Edgewater, FL
I found a working Hitachi V1100A on Craigslist for $100.....

drjim - I could always ship this thing to you and let you play with it... LOL....