Topics

A Couple Restorations


greenboxmaven
 

My main pleasure with equipment is finding inoperative or basket cases and restoring them. I just finished a 2230 and an R-631B. This is an account of the projects, skip now if you aren't interested.

The R361B was obtained from a member of this group, and I was quite pleased with it when it arrived. I replaced the power cord, and tried it out. It came alive, had a trace, then a loud snap was heard and it went dead. I feared the worst, but continued with the work. It needed a bath, and got it, followed by about ten hours in a hot box to dry it out. I wanted to see if I could get the power supply working before I put the jug back in after the cleanup. First tests were aweful. None of the voltages were correct. The negative 100 volt supply is the reference for everything else, and it was producing about 115 volts. All of the others were very low. After a few hours of round and round circuit tracing, I found the key problem- a partially shorted ceramic condenser. It was one of the square red Erie brand ones, rated at 200 volts. There were two on the board, I replaced them with 600 volt ceramic discs. There were two other old electrolytics, I changed them out as well. The fuse protecting the high voltage supply was gently blown, not fried and flashed all over the glass tube. After finding and replacing two fried transistors in the positive 125 volt supply, everything came alive and right on what they should have been. I put a fuse in the high voltage supply, it came alive with an output nearly 4KV, it should have been 3300. I turned the HV adjustment all the way down, but could not get it below 3500. Both of the transistors in the HV regulator are "special selected", and tested good. After studying the manual, and not having exact original transistors, I added a 12 meg resistor in parallel with the 2.2 meg resisator coming from the moving contavt on the HV adjust pot. That allowed me to adjust down to 3300 volts. I cleaned all the switches and pots in both the mainframe and plug ins, re-installed the jug, and tried it out. With adjustment of the sweep and position controls, I was rewarded with a good bright trace. External signals and the built in calibrator were displayed quite well. The vertical plug in I have is a single trace differential, not especially useful to me, so I have a 72 dual trace on order. I will let the scope cook on the bench for another day or so before I put it aside waiting for the dual trace preamp to arrive. It will probably be used in my RTTY setup, the vertical response is only about 600 KC.

The 2230 was a genuine basket case, almost entirely dismantled and filthy with carbon dust. It was a freebee with another purchase at the Rochester hamfest. I was quite skeptical until I got it home and found that except for many screws, it was complete. It wasn't stored in the dirt, it was operated in the filth because the knobs and front panel were almost unreadable, and the focus pot was completely covered in fuzz. Getting the front panel and control label plastic sheet off took a bit of exploration, but WD-40 and a blow dryer softened up the adhesive on the sheet, and it came off with very little damage. Now I could remove the front panel to give it the cleaning it needed. Now fully dismantled, everything got a bath. The cleaner and rinse water were black as night, but everything cleaned up very well. After re-assembly, cleaning and lubing switches and pots, it was time to see if it would come alive. Turning the power on did nothing for a second or so, but the pilot lamp blinked and the cooling fan moved. I remembered a similar problem with broadcast waveform monitors and vector scopes, and replaced all of the smaller low voltage electrolytic condensers in the circuit that drives the inverter. Now, the same delay but the fan started and the pilot lamp lit. There were some bright green blobs on the screen, adjustement of the focus control produced brilliant menu text. After exploring the controls, I found that one of them had to be pushed in to display waveforms. I spent an hour or so exploring the locking action of the pushbuttons, and there was no was to get two of the switches to latch in, even if I borrowed the latch pins from other switches. The others that were supposed to latch did. Because the buttons are plastic stems on the switches, I filed a notch in the bottoms of the two that would not latch. This allowed them to latch in, a gentle lift released them. Everything seemed to work fine, the scope has many features I will probably never use, but it displayed waveforms and would store them. After several hours of cooking, I put the shield cover over the power supply section and the brace that supports the top circuit board back in. I turned it on, and was met with a total disaster. The only thing I could get on the screen was blobs bouncing around. I shut it off instantly, and started looking for bad solder joint on the bottom board where the power supply is located. A solder splat was found and removed, the scope came on and performed fine. After a few more hours of cooking, I put the case and back panel on and ran it on test for a few more hours. It performs very well, it will probably be used mostly in my shack to troubleshoot RF circuits and monitor transmitter outputs because it has a 100 MC. vertical bandwidth.

These are examples of the kind of projects I really like. Now, does anyone have a 224 handheld scope project they would like to find a home for? 73.

Bruce Gentry, KA2IVY


-
 

Bob,

Where are you located? there is a small handheld Tektronix scope in a
surpus store near me and that I can probably get cheaply. As best as I can
remember it is a 2xx model but I don't remember the complete model number.

On Wed, Nov 25, 2020 at 10:09 PM greenboxmaven via groups.io <ka2ivy=
verizon.net@groups.io> wrote:

My main pleasure with equipment is finding inoperative or basket cases
and restoring them. I just finished a 2230 and an R-631B. This is an
account of the projects, skip now if you aren't interested.

The R361B was obtained from a member of this group, and I was quite
pleased with it when it arrived. I replaced the power cord, and tried it
out. It came alive, had a trace, then a loud snap was heard and it went
dead. I feared the worst, but continued with the work. It needed a bath,
and got it, followed by about ten hours in a hot box to dry it out. I
wanted to see if I could get the power supply working before I put the
jug back in after the cleanup. First tests were aweful. None of the
voltages were correct. The negative 100 volt supply is the reference for
everything else, and it was producing about 115 volts. All of the others
were very low. After a few hours of round and round circuit tracing, I
found the key problem- a partially shorted ceramic condenser. It was one
of the square red Erie brand ones, rated at 200 volts. There were two on
the board, I replaced them with 600 volt ceramic discs. There were two
other old electrolytics, I changed them out as well. The fuse protecting
the high voltage supply was gently blown, not fried and flashed all over
the glass tube. After finding and replacing two fried transistors in the
positive 125 volt supply, everything came alive and right on what they
should have been. I put a fuse in the high voltage supply, it came alive
with an output nearly 4KV, it should have been 3300. I turned the HV
adjustment all the way down, but could not get it below 3500. Both of
the transistors in the HV regulator are "special selected", and tested
good. After studying the manual, and not having exact original
transistors, I added a 12 meg resistor in parallel with the 2.2 meg
resisator coming from the moving contavt on the HV adjust pot. That
allowed me to adjust down to 3300 volts. I cleaned all the switches and
pots in both the mainframe and plug ins, re-installed the jug, and tried
it out. With adjustment of the sweep and position controls, I was
rewarded with a good bright trace. External signals and the built in
calibrator were displayed quite well. The vertical plug in I have is a
single trace differential, not especially useful to me, so I have a 72
dual trace on order. I will let the scope cook on the bench for another
day or so before I put it aside waiting for the dual trace preamp to
arrive. It will probably be used in my RTTY setup, the vertical response
is only about 600 KC.

The 2230 was a genuine basket case, almost entirely dismantled and
filthy with carbon dust. It was a freebee with another purchase at the
Rochester hamfest. I was quite skeptical until I got it home and found
that except for many screws, it was complete. It wasn't stored in the
dirt, it was operated in the filth because the knobs and front panel
were almost unreadable, and the focus pot was completely covered in
fuzz. Getting the front panel and control label plastic sheet off took a
bit of exploration, but WD-40 and a blow dryer softened up the adhesive
on the sheet, and it came off with very little damage. Now I could
remove the front panel to give it the cleaning it needed. Now fully
dismantled, everything got a bath. The cleaner and rinse water were
black as night, but everything cleaned up very well. After re-assembly,
cleaning and lubing switches and pots, it was time to see if it would
come alive. Turning the power on did nothing for a second or so, but the
pilot lamp blinked and the cooling fan moved. I remembered a similar
problem with broadcast waveform monitors and vector scopes, and replaced
all of the smaller low voltage electrolytic condensers in the circuit
that drives the inverter. Now, the same delay but the fan started and
the pilot lamp lit. There were some bright green blobs on the screen,
adjustement of the focus control produced brilliant menu text. After
exploring the controls, I found that one of them had to be pushed in to
display waveforms. I spent an hour or so exploring the locking action of
the pushbuttons, and there was no was to get two of the switches to
latch in, even if I borrowed the latch pins from other switches. The
others that were supposed to latch did. Because the buttons are plastic
stems on the switches, I filed a notch in the bottoms of the two that
would not latch. This allowed them to latch in, a gentle lift released
them. Everything seemed to work fine, the scope has many features I will
probably never use, but it displayed waveforms and would store them.
After several hours of cooking, I put the shield cover over the power
supply section and the brace that supports the top circuit board back
in. I turned it on, and was met with a total disaster. The only thing I
could get on the screen was blobs bouncing around. I shut it off
instantly, and started looking for bad solder joint on the bottom board
where the power supply is located. A solder splat was found and removed,
the scope came on and performed fine. After a few more hours of cooking,
I put the case and back panel on and ran it on test for a few more
hours. It performs very well, it will probably be used mostly in my
shack to troubleshoot RF circuits and monitor transmitter outputs
because it has a 100 MC. vertical bandwidth.

These are examples of the kind of projects I really like. Now, does
anyone have a 224 handheld scope project they would like to find a home
for? 73.

Bruce Gentry, KA2IVY