Dueling Heathkits
 

I saw an ad for a GR-2000 not far from me, no cabinet. I got it from a fellow who built it in 1979 and was considering taking it to the recyclers. He said it was mounted in a wall and that he built 13 of them back in the day. Just as I was about to leave with the set he said he had another I could have for free. Considering the weight of the 2000 and I could take only one big set on my trolley at a time, I kind of hoped it was a portable. Down to the basement we went where a GR-370 in a console cabinet with a power VHF tuner was sitting next to a washing machine. It was filthy and the finish on top trashed, probably from jugs of laundry soap sitting on it over the years. I couldn't pass it up so I offered to come back for it and left, walking over four kilometers in light snow before being offered a ride the rest of the way. Another guy was there the next time, probably the owner's son, who helped me lug it up to the main level. We plopped it onto my trolley and away I went, 7 kilometers back home.

The 25VEDP22 in the 2000 tests almost new. The 25BCP22 in the 370 is pretty weak. It's such a cool set though that it's worth a replacement CRT. They're mostly complete; all that's missing is a remote for the 2000, a channel knob and power button for the 370, and the 370's volume knob is broken. The lower panel is warped badly, causing the entire chassis with attached CRT to tilt backward. I'm not sure what I'm going to do about a case for the 2000.

Now for the tricky part: I know next to nothing about these sets, whether it's safe to attempt to power them up for one thing. I don't know where to start.

Pics of the GR-2000:
https://www.flickr.com/photos/154129...57687971372025

Probably OK to just plug in. These sets used RCA SCR
sweep so that part quite reliable. I dont know if its OK
to bring it up slow without removing them. Never had to.

73 Zeno:smoke:
LFOD !

I've got 2 Heathkits, one is a GR2000 and the other is a GR2001. One has a cabinet and the other is on a dolly.
A while back I converted them to video input, bypassing the tuner and IF. They make a better picture now since you're not bandwidth limited by the IF strip.
Heathkits are really collectors items since it was a kit TV.

To err on the side of caution, I'll probably remove the SCR sweep module anyway. Since these are SS sets, but unusual ones, is there anything I need to know when starting them with a variac?

The fellow said the GR-370 had some kind of vertical problem but I forget what. The vertical oscillator has been replaced; the old one was floating around in the cabinet. The loose one uses carbon composition resistors on it whereas the replacement uses carbon film.

Was offered a free 2000 at radiofest 'bout 3 years back wanted to get it, but space was low and time was critical.

SCR sweep is something I never wrapped my head around.
findemkeepem seems to have a good feel for them. I did
lots of RCA's & some Philcos & fortunately never had a dog.
Worse thing was a bad H osc board blowing one of the SCR's.

Slow start without sweep will only prove out the PS & probably
the low level stuff. Sweep problems are where slow start shines
on SS TV's. Just never had to do it on an SCR set so not sure
if its safe.

A few hints for slow start. Using a Power Rite or eq on SS sets......
1) unplug the degauser. It draws a ton of current at start & can
even pop the breaker on the power rite.
2) start at 75V & slowly raise til it starts. Watch the meter !
Keep it under 2A. As you turn it up the current should slowly
drop til its in the .75 - 1 amp range.
3) If current goes UP with voltage use all your senses to find
the problem. FEEL the HOT, SMELL for burning & arcing.
LOOK for puss coming out of FBT or abnormalities in the
raster , smoke. LISTEN for crackling. Also if normal before you raise
voltage tap around especially the H osc & H. drive.

Thats the short story. A book could be written on other techniques
& procedures such as when to jump the ON/OFF relay, sub a
start voltage etc. Thats what this list is for.

73 Zeno:smoke:
LFOD !

I brought the 370 up to full line voltage without catastrophic failure. I get audio but nothing on the screen. The HV area gets warm and ticks a little. I stuck my HV probe in place and switched the Powerite back on; the HV isn't completely dead but the indicator barely moves.

The 2000 I was more comfortable running at full line voltage right away. Nothing, totally dead. Checked the breaker, it hadn't popped.

Never had any trouble with the SCR sweep. But did lose a cap in the vertical section once.
If its not turning on, I'd check the thermistor on the power supply board. The have a tendency to unsolder themselves.

I checked the module, looks as if there's a part missing. Does the attached look familiar?

By the way, installing A/V jacks is a neat idea. Heathkits were made for hobbyists, so why not?

No
 

Those are the pins for the degaussing coil connection (on the bottom of the board). But that transistor looks like its cocked in its socket maybe not making connection.
I'd pull the board and check the solder connections.

She's a runner!
 

I straightened out and re-seated the transistor on the power supply board, pulled the board to check the solder connections, no dice. However, when I was looking at the board on the back of the service drawer I saw two mashed-over transistors, one with a lead out of its socket. Corrected that, hit power and bingo, full bright raster with snow.

The power button won't turn it off though and the OSD doesn't work, so I'm going to have to poke around some more. There's a busted coil on the chroma board, got to find out the correct replacement.

Gr2000
 

There's a master power switch under the control panel door. Think its mounted on the contrast control.
There's also a jumper on the display board that enables/disables the display.
Your set may or may not have the clock module. It was an option.

The volume control turns it on and off, I assume that's normal.
The jumpers are soldered in but I discovered another cocked transistor. Display is working now.
It does have a clock, also working.

Looks like the sets been slapped around a bit ! Agree with
KF4RCA, nice call BTW ! ( de KA1YHI) Looks to be DGS socket
with one pin broken off. Also the thermistor looks pretty toasted.
If it opens the set will run through the big VDR & it will
brew up with much smoke & dripping mung. Probably 120 ohms
cold but check the manual.
If this uses the RCA vert out design IIRC it uses a yoke coupling cap.
Typically a 470 mfd 200 V. It hooks between the two vert outs
& the yoke. Causes anything form small to zero vert sweep.
Also used in cheap to mid line stereos & a common fail.
A SS vert amp & out are no different than an audio amp & out
often.........

73 Zeno:smoke:

Yup, but no rust, no cabinet rot in the 370 and nearly complete. I guess the 370 just sat so long the weight of the chassis and CRT warped the particle board. Mocking up a replacement will be easy, it's not something readily visible so I'll make it from plywood. Got to strip and refinish the cabinet.

Any safety cap issues with these? Also, is there a place I can download manuals? I got zero documentation with these.

Is the thermistor that big black disc? I think it's fine, it was just caked in dust.

No, the thermistor is the little bitty metallic looking disc next to it. If it goes open, the big black thingy (VDR- voltage dependant resistor, or varistor) will cook, fry, sizzle, smoke, and drip stinky mung. Hey, learned a new word from Zeno.:lmao:

Oh well, I doubt it would out-stink a blown selenium rectifier, or even come close to that.

I wiped off both discs. Not sure what to think of the thermistor...

Figured out the oddball varactor tuner/OSD and got it on channel 3 for a DVD feed. I hooked up a speaker, sound works. It looks pretty bad, but it's a start.

That is NOT a bad start ! Strong jug. Looks like blue convergence
is way off on bottom right.

73 Zeno

Ah, I didn't mean it was a bad start, just that it looks kind of bad because I haven't done any setup adjustments. :) I just changed a couple of jumpers and dialed in the channel. Often times the picture gets skewed horizontally or shifts vertically so that the two halves of the image are in the wrong places, but hey, it's working. :thmbsp:

One of the problems with those modular sets is intermittent connections. When you put the set in its final position, you need to re-seat all the modules.
At one time, all manufacturers made modular sets. But it was soon discovered that all the connections created intermittent problems. So they returned to a unitized chassis design.
To create a video input, you'll need to go in at the emitter of Q312 with 3.5 Volts P-P on non-inverted video.

I'll do that, and re-seat the ICs and other transistors as well. May as well try the same with the 370, it may get high voltage back. If not, who knows what other ills it has that might be cured.

I found a S-video mod for the 2000, I'll probably go all out and try that.

Had a heath scope that had issues with IC socket intermittents, before I was acquainted with contact cleaner...Did not keep it long.

What coil did you say was broken? If its on the IF board, you may not need it if you are going to convert to A/V input.
For a video input, you can use a video buffer IC or you can use 2 transistors. One transistor will not do it since you need more than 1V of video. An emitter follower will give non-inverted video but with no gain. So you will need a two transistor design called a compound pair.
Here's the circuit I used.

Excellent, thanks.

The broken coil is on the chroma board.

If it is JUST a coil and not a transformer, then you may be able to rewind it. just unwind, glue the form back together, and rewind.

If that doesn't work, you can probably salvage a coil from an RCA of the same vintage.

I'd rather put in another one really. Would one from a CTC-88 work? I have one from September 1978. I wouldn't be junking it, just borrowing a coil. Also, are there any Heathkit manuals available for download?

Its probably the coil. It sticks out like a sore thumb. The transformer has a shield around it.
Most likely the CTC-88 coil will work. The chip used is an RCA CA3071. It was also manufactured by Motorola as the MC1371. It was part of a very popular chipset:
http://www.ralphselectronics.com/pro...EMI-CA3071.PDF
The manuals are assembly for the most part and since yours is already assembled, they're not needed. The schematic is a large 24x30 sheet.
BUT that set is legacy technology so you shouldn't need a schematic.

The coils in the CTC-88 look a little small. The base of the broken one is marked 40 with 1649 under that. Any idea what would replace this?

Thats probably the Heathkit part number. The coil could be smaller depending on the value of the cap thats across it. Probably have to keep those two together when substituting.
Is there no way you can repair L451?

He'll have to try before answering that...accurately.

This is a good circumstance to learn. The old part don't work and there is nothing to loose by trying to fix it...If you are thinking you need a new one anyway, then trying to mend the original looses you nothing.

I have something in mind and will try it very soon. I had to look back on my lifetime training in redneck engineering for a possible solution. The wiring is still intact and the slug is still there, so it's probably functioning.

On a side note, I've been digging into the GR-370 again. I hooked it to my DVD player and got clear sound, but on an adjacent channel so perhaps someone messed with the IF stage. I did find a diddle stick in there. Also, to my surprise, it has a HV rectifier tube, a 3A3C. I can draw an arc from the fly lead, but the tube shows no signs of life. It isn't gassed out though. Might the tube be bad, or could it be something else?

Does the heater have continuity? Does the fly heater winding supply enough voltage? do you have a tube tester or another working set that uses that tube?

Possibly open filament... if you don't have a tube checker, check the filament resistance between pin 2 and pin 7, it should be around 2 ohms or less. I just measured one at 1.78 ohms.

jr

Can you see the filament glowing in the neck of the tube?

No glow, filament seems fine, no reading when checking filament voltage. My meter has been having problems, but I hooked it to a power supply and it checked fine on the same range.

Does your answer pertain to the CRT heater or the 3A3 filament?

jr

You usually wont see a HV rect light up. After running a while
it will get quite warm. Odds are the tube is bad. Many early
SS sets ( Moto, RCA, Sony ) used a tube & they went often.
Sony was an exception probably cause they used a 25KV tube
in a 12" set.

73 Zeno:smoke:
LFOD !

Oh, the 3A3 filament. The CRT heaters are lighting. I did notice some purple arcing in the 3A3 though.
Actually I did notice the HV cage get warm after a little bit when I first started the set.