On Sun, 26 Jun 2005 01:15:01 -0400, beerbarrel
wrote:

Picked up a HP 8640B for a song. When I powered it up, the counter
display was inop. After removing the cover, I noticed that the LED for
the 5V regulator card was not lit. I removed the card and found that
the fuse was blown. Well, needless to say, the new fuse blew
instantly. My question is this: Has anyone ever torn into one of these
that might have had this problem? I thought that I might ask before I
dug any deeper.

Thanks,
Tracy

First thing is to check the 5V bus for a short. If that is OK then
check the regulator card and external pass transistor for problems.
A little patience and I'm sure you'll find the problem. Good luck.

Nanu

beerbarrel wrote:

Picked up a HP 8640B for a song. When I powered it up, the counter
display was inop. After removing the cover, I noticed that the LED for
the 5V regulator card was not lit. I removed the card and found that
the fuse was blown. Well, needless to say, the new fuse blew
instantly. My question is this: Has anyone ever torn into one of these
that might have had this problem? I thought that I might ask before I
dug any deeper.

Thanks,
Tracy


the power transistor on the botton side comes loose! tighten the
screws, also check for bad caps. other than that if you got the
doubler option for 1 Ghz, you have something there.
its an easy thing to repair/

beerbarrel wrote:

On Sun, 26 Jun 2005 17:20:39 -0700, Jamie
wrote:


beerbarrel wrote:


Picked up a HP 8640B for a song. When I powered it up, the counter
display was inop. After removing the cover, I noticed that the LED for
the 5V regulator card was not lit. I removed the card and found that
the fuse was blown. Well, needless to say, the new fuse blew
instantly. My question is this: Has anyone ever torn into one of these
that might have had this problem? I thought that I might ask before I
dug any deeper.

Thanks,
Tracy


the power transistor on the botton side comes loose! tighten the
screws, also check for bad caps. other than that if you got the
doubler option for 1 Ghz, you have something there.
its an easy thing to repair/



Found out that emitter to collector was shorted in the pass
transistor. They are very easy to replace. I noticed that it had been
replaced before at some point. They used a mica insulator between the
transistor and ground. The insulator was broken. I think the collector
might have been grounded. I had a 3055 to replace it. Now I just have
to get some of those hard to find little fuses that solder onto the
regulator card. I only have 35 dollars in the generator so if it never
works I'm not out too much.

Thanks,
Tracy
i have 2 of those units with the 1 Ghz option.
old but very nice with the hard line feeds in side ect. )
P.S.,
make sure you lubricate the range selector universal because the
original grease (safe for plastics) tends to harden up. also check for
alignment and make sure there isn't any slack between the joints.

beerbarrel wrote:

On Sun, 26 Jun 2005 17:56:08 -0700, Jamie
i have 2 of those units with the 1 Ghz option.
old but very nice with the hard line feeds in side ect. )
P.S.,
make sure you lubricate the range selector universal because the
original grease (safe for plastics) tends to harden up. also check for
alignment and make sure there isn't any slack between the joints.



Dumb question time...how do ypu ID the card that has the 1 ghz option.
As of yet, I have not powered up the unit for more than a few seconds.

Thanks for the tips. I also found info on the problems with the delrin
gears.

Tracy
Hmm, i not sure about that, i also got these 2 units from ebay, the
selector dial has the 1024 position on it, when you snap the switch over
to the mode your freq counter should display it.
as far as i know its simply a doubler module put in there.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

In article , beerbarrel
wrote:

It does have the 1024 range on the switch. Maybe that's a good sign
eh?

Tracy-

Apparently the doubler can be added to one that doesn't have it. As I
recall, the internal counter displays frequencies in the 1024 range, even
if the doubler is not there. I have the impression that the counter is
not connected to the output, but to an earlier stage, and displays a
calculated value.

Look at the HP label that has "OPT" and see if any are listed. I think
the doubler is option 3.

If you need a manual, do a search for TM 9-4935-601-14-7&P.pdf. It is
about 10 Megabytes.

Fred

beerbarrel wrote:
On Sun, 26 Jun 2005 01:15:01 -0400, beerbarrel
wrote:


Picked up a HP 8640B for a song. When I powered it up, the counter
display was inop. After removing the cover, I noticed that the LED for
the 5V regulator card was not lit. I removed the card and found that
the fuse was blown. Well, needless to say, the new fuse blew
instantly. My question is this: Has anyone ever torn into one of these
that might have had this problem? I thought that I might ask before I
dug any deeper.

Thanks,
Tracy



I replaced the pass transistor. I installed a 5 amp fuse. It calls for
a 3 amp. I did not have one so that will have to wait a few days. The
transistor runs mighty hot. Is that normal for this particular
generator? It seems to work fine though. I noticed whomever replaced
the last transistor did not use any conductive paste. I'm thinking
that may be some of the heat issue.

Tracy
mine does not run hot, you mite want to check for leaky caps.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5