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NAP PTV300 Chassis Interchange?

K

Kirk S.

Jan 1, 1970
0
Hello again,

I've got a Magnavox RH8524AK08 projection TV that went dead. I bought a set
of boards from an RH8520 from a guy on eBay. The power supply board
indicated in my service manual is the same for both sets (APW007). The
flyback is totally different on the set that I bought; my original has a
tube that comes out at an angle that the HV line slips into and a nut
tightens down. Since the set I bought came with the HV line and splitter, I
replaced the associated parts as well. The TV now comes on. I'm going to
replace the crt coolant before doing anything else. The other boards
(deflection, etc) are the same in both sets. The old flyback is part
362003-0005 which seems to be out of production. The new flyback is
362140-1. The replacement board has an outline on the PCB that matches the
old format.

Is this going to cause a problem? Given the age of the set, is it likely
the power supply was changed at some point? Also, where can I get
replacement crt seal kits so I can change the coolant?

Thanks for any help keeping this dinosoar alive...

Kirk S.
 
J

John-Del

Jan 1, 1970
0
The new type flyback is more reliable than that old chunk it replaces.
As for there being any potential problems in the future? Well, it's a
PTV300. You've been playing on bonus time for many years now.

You won't need new seals when you change the coolant. Just get the
coolant changed before the replacement boards crap out.....

John
 
B

Bill S.

Jan 1, 1970
0
I've got a Magnavox RH8524AK08 projection TV that went dead. I bought a set
of boards from an RH8520 from a guy on eBay. The power supply board
indicated in my service manual is the same for both sets (APW007). The
flyback is totally different on the set that I bought; my original has a
tube that comes out at an angle that the HV line slips into and a nut
tightens down. Since the set I bought came with the HV line and splitter, I
replaced the associated parts as well. The TV now comes on.

It's unusual to find one of those relics that still works. We used to
call them "gourmet flybacks from Orville Reddenbacher", you know - not
a one left unpopped ;-) A slight exaggeration, no doubt, but a *lot*
of them blew up. I guess if you have one that survived this long, no
reason not to keep using it.

Another common problem about that vintage was green circuit boards
that used square pins shoved through the board for feed-throughs
instead of plated-through holes. This attempt at cost cutting was a
notorious source of intermittant connections. Some were so bad that
they required repair right out of the box before they could even be
sold.
Is this going to cause a problem?

Aside from the questionable reliability of certain parts already
mentioned, I don't see a problem. There were minor variations for
special versions like the JBL sound system, but basically they were
intended to be compatible. As you have discovered, the HV lead is
different, so just use the one that came with it.
Given the age of the set, is it likely the power supply was changed
at some point?

Fair chance. We used to carry a set of spare boards in the service
truck for elusive problems. Sometimes easier to swap in the home and
rebuild back at the shop where presumably you have better lighting,
more tools, parts, and equipment.
Also, where can I get replacement crt seal kits so I can change the
coolant?

The O-rings between the lens and the cooling chamber are quite durable
and usually reusable. I have not often needed the gasket between the
CRT and cooling chamber except on the rare occasion of replacing a
tube. Philips didn't list these parts separately in the manuals, but
shows one each as parts of the 171677-3 kit. I used to have the
individual numbers written down somewhere but can't find them anymore.
 
K

Kirk S.

Jan 1, 1970
0
Bill S. said:
It's unusual to find one of those relics that still works. We used to
call them "gourmet flybacks from Orville Reddenbacher", you know - not
a one left unpopped ;-) A slight exaggeration, no doubt, but a *lot*
of them blew up. I guess if you have one that survived this long, no
reason not to keep using it.

Unfortunately, the dead flyback is one of the angle HV connector types.
Found a sticker in the bottom of the set: 3620030005. Have found similar
ones for 3620030006/7. The newer board had the 352140-1 flyback on it.
Guess I can just repair it if (when) it blows.
Another common problem about that vintage was green circuit boards
that used square pins shoved through the board for feed-throughs
instead of plated-through holes. This attempt at cost cutting was a
notorious source of intermittant connections. Some were so bad that
they required repair right out of the box before they could even be
sold.

Yep, the convergence board required resoldering of these square pins. Had a
blue ghost that would appear and disappear when the set warmed up. The old
p/s board is green with those nasty square pins. I reflowed some fresh on
the convergence board and that took care of the problem.
Aside from the questionable reliability of certain parts already
mentioned, I don't see a problem. There were minor variations for
special versions like the JBL sound system, but basically they were
intended to be compatible. As you have discovered, the HV lead is
different, so just use the one that came with it.

Would it help to replace the electrolytic caps on the deflection and power
supply boards?
Fair chance. We used to carry a set of spare boards in the service
truck for elusive problems. Sometimes easier to swap in the home and
rebuild back at the shop where presumably you have better lighting,
more tools, parts, and equipment.


The O-rings between the lens and the cooling chamber are quite durable
and usually reusable. I have not often needed the gasket between the
CRT and cooling chamber except on the rare occasion of replacing a
tube. Philips didn't list these parts separately in the manuals, but
shows one each as parts of the 171677-3 kit. I used to have the
individual numbers written down somewhere but can't find them anymore.

What sort of sealer/lubricant should I use on the o-rings? Or, should I
just clean out the crud the best I can, replace the coolant (with the set
angled so the crt in question is level) and see what sort of improvement I
get?
Thanks again for the advice. The cabinet on this thing is so nice that I'm
having a hard time getting rid of it.

Kirk S.
 
B

Bill S.

Jan 1, 1970
0
Unfortunately, the dead flyback is one of the angle HV connector types.
Found a sticker in the bottom of the set: 3620030005. Have found similar
ones for 3620030006/7. The newer board had the 352140-1 flyback on it.
Guess I can just repair it if (when) it blows.

Sorry I misunderstood your message, I thought you were saying you had
one of the angled type still working.
Would it help to replace the electrolytic caps on the deflection and power
supply boards?

They didn't seem to be a big problem on these boards. If you have an
ESR checker, you could test them while the board is out. Or if they
have leaked or gotten hot.
What sort of sealer/lubricant should I use on the o-rings?

They don't use any sealer. Be sure to clean the groove and "C" element
surface squeaky clean. The glycol solution cooling fluid is plenty
slippery.
Or, should I just clean out the crud the best I can, replace the coolant
(with the set angled so the crt in question is level) and see what sort
of improvement I get?

You'll probably see what is going on as you disassemble the things.
The lens assemblies can be removed anytime (four 1/4" screws), but you
will want to suck or drain most of the fluid before removing the "C"
element (larger nuts), or you will make a big mess. Once the "C"
element is out, you can clean the inside of the chamber with toilet
tissue, paper towels, etc. For stubborn encrustation, you can use
alcohol, windex, etc. Finish up with something lint free.

Once you have things clean you can remount the "C" element and fill the
tube. You will need to have the tube angled like normal operating
position if you left it in the set, or on its side if you pulled it.
With the tube level you will not be able to get enough of the air
bubble out of it.

Do the blue tube first, it's always the worst and will give you the
most noticeable improvement. The green and red will then seem easy.
 
K

Kirk S.

Jan 1, 1970
0
Bill S. said:
Sorry I misunderstood your message, I thought you were saying you had
one of the angled type still working.

Well, it "was" working until it died. Been reading about "ringing" a
flyback using an o-scope and the calibration setting. Looks like a good
chance to practice on a bad one.
They didn't seem to be a big problem on these boards. If you have an
ESR checker, you could test them while the board is out. Or if they
have leaked or gotten hot.

None look like they are leaking/bulging so I won't break it by fixing
them...
They don't use any sealer. Be sure to clean the groove and "C" element
surface squeaky clean. The glycol solution cooling fluid is plenty
slippery.


You'll probably see what is going on as you disassemble the things.
The lens assemblies can be removed anytime (four 1/4" screws), but you
will want to suck or drain most of the fluid before removing the "C"
element (larger nuts), or you will make a big mess. Once the "C"
element is out, you can clean the inside of the chamber with toilet
tissue, paper towels, etc. For stubborn encrustation, you can use
alcohol, windex, etc. Finish up with something lint free.

Once you have things clean you can remount the "C" element and fill the
tube. You will need to have the tube angled like normal operating
position if you left it in the set, or on its side if you pulled it.
With the tube level you will not be able to get enough of the air
bubble out of it.

Great... Sounds like I can do it in the set. I'll get an idea how much is
in the chamber when I suck it out. Got two 24oz bottles from MCM. Hope
it's enough...
Do the blue tube first, it's always the worst and will give you the
most noticeable improvement. The green and red will then seem easy.

I'll follow your instructions about convergence, screen, cutoff, etc...

I'm sure that I'll be back for more brainpicking. Learning about this stuff
is very interesting.
 
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