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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Thu 19, 2022 3:38 am 
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For the CRT tester, the fact that the calibrate adjustment does anything indicates that that part of the circuit is basically working. It may be normal for the transformer to buzz at certain settings.
There are a bunch of adjustment pots on the circuit board. The problem could be that they are dirty and need to be cleaned. You would have to carefully mark their current positions and then clean them with contact cleaner. Rotate them back and forth a bunch of times and then put them back exactly where they are now. Also clean the various switches.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Thu 19, 2022 8:38 am 
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Sprayed and rotated the pots around and back to original positions, no change. The neon lamp inside lights up and warbles around depending on the Calibration knob. So at least the lamp works. I'm guessing it is used in the circuit somehow other than to just light up since it's inside.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Thu 19, 2022 3:18 pm 
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Frenchmarky, maybe you didn't describe what you did with trying to operate the tester, but after reading the manual I wonder if you were operating it right. You use the meter to read the line voltage and then according to the reading you adjust the cal knob to bring the needle to the correct cal mark. You don't adjust it to get a particular voltage. Without the manual you might have never operated it correctly, then again maybe 20 years ago you did have the manual. Maybe you should take a look at the manual.
From the schematic the neon pilot lamp also functions as a voltage regulator. There may be a problem with the circuit. Unfortunately neon bulbs do not last forever and I think this one is a special type since it also functions as a regulator.

The line adjustment control is a bit unusual in that it adjusts the power supply by using an AC phase control circuit. That is like a lamp dimmer circuit. A phase control circuit changes the shape of the power AC voltage, that can cause buzzing and results in a waveshape that is not a sine and therefore will not read correctly on a normal AC meter. The reason I mention that is that I noticed that the tester calibration procedure to adjust the internal pots specifies using a "vane" type meter. A vane type meter does measure a non-sine AC voltage correctly, it is a "true RMS" reading meter.

I doubt that your TV problem is due to the CRT anyway.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Thu 19, 2022 6:29 pm 
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Ohhh shoot, I *was* making an error with the calibration marks, it does go to the correct mark. I was using the same line voltage marks. Although I definitely would have been concerned with this thing buzzing loud like that when I used it back then so that is new. Lemme give it another shot this afternoon. Thanks for discovering my goof. (My brain is 25 years older now too!) :)

Update- test of CRT looks great, HK leakage just a hair above zero, G1 leakage zero, passed cutoff test fine and emission is beyond halfway into the green. The new caps in the tester do seem to have helped a little bit as the power lamp stays on now and doesn't turn off if Calibration is cranked up. I'll check my regular tube tester for old elec. caps too.

This may be a replacement tube as somebody scribbled '12KP4' on the chassis with a pencil, but I can't find the number on the tube. On to pulling the chassis.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Fri 20, 2022 7:46 am 
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I remembered something confusing about this 10” pic tube way back when I replaced the capacitors:

- Model 2291 is listed on radiomuseum as having a 10 inch tube - but it’s a table model and mine is stamped 2291 but it’s a floor model (?)
- The photofact parts list for models 2291 thru 2298 (same chassis) list 10 & 12” tubes but not which set used which tube
- The mounting strap looks too big, someone had to stuff styrofoam in the bottom gap to take up the slack and raise the face of the tube, as if the set originally had a 12”
- But the 10” tube and the rubber gasket do completely fill the hole in the cabinet

Then I noticed the 12KP4 note scribbled on the chassis. So I am still confused as to whether this set originally had a 10” or a 12”. (?)


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Fri 20, 2022 4:05 pm 
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Upgrading the size of the screen as new CRTs became available was not uncommon at one time.
So a chassis originally designed for a 10" could sometimes work with a 12" for instance. I believe new masks were available to allow this sometimes.
The Styrofoam block might be a replacement for something that crumbled away.
I suppose if a 12" needed to be replaced and the repair shop didn't have one they might put a smaller one in (with the customer's consent). Also the customer might have wanted to get by with the smaller one to save some money. With anything that's been around a long time who knows what the history of it may be. If these things could talk.
If you wanted to make sure the set is as it was as it left the factory (suitable for a museum, etc.) you could do more research into it and if it isn't right you could change the CRT.
I doubt you would want to do that.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Fri 20, 2022 5:48 pm 
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Also could be that the original chassis for your cabinet had a major meltdown and a good chassis from a 12" set was installed as a replacement. They then had to adapt it to the 10" opening in your cabinet.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Fri 20, 2022 8:38 pm 
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I'm leaning towards it had a 12" originally and was replaced with the 10" as suggested. A 12" would fit the hole too but would be 100% screen and no rubber gasket. Looks like they sold two different escutcheons around the screen, for 10" and 12", and this one probably still has the one for the 12". No big deal, the gasket doesn't bother me.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sat 28, 2022 2:34 am 
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Getting back to this one, I was sliding the chassis out to test the tubes etc. and noticed a factory label inside the cabinet plain as day that I didn't pay attention to years ago. It lists two models for this cabinet, #2291 w/ 10" tube and the #2295 w/ 12" tube, so the 10" I have in there is actually correct since the cabinet is stamped 2291.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sat 28, 2022 8:04 am 
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Tubes all tested green on my tester, sprayed the front controls. Looks like back during my re-cap I had tested nearly all the resistors in circuit and if they were good or close enough I marked them with a dot, otherwise if was too high I checked them out of circuit and if too high I replaced them with the blue ones. Geez I barely remember any of it. Resistor tied between the brightness and contrast control is new, tests good. No swelling in the electrolytics. Not sure what area in the schematics I should be focusing in on further that could cause the contrast issue, like what caps might have gone bad. Continuing testing resistors and next will start checking pin voltages.

With no input plugged into it, the set can be dialed down to an 'off' screen, but not when watching anything on it.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sat 28, 2022 8:24 am 
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I would investigate the peaking coils and the others forward of the detector(6AL5), make sure none are open or high resistance. These coils corrode open sometimes from the glue or moisture in the atmosphere. A quick visual check would be look for any that the windings have turned green or black, test any suspected. A bad peaking coil can cause video issues and they take a few minutes to check.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sat 28, 2022 11:24 am 
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Will do, thanks.

I'm doing the resistance measurements of all the tube pins vs. the chart in the schematics also, never needed to try that before. Is there a rule of thumb as far as how close the readings need to be to the chart? Example, say three pins on the chart specify they should be 100K ohms, zero ohms and 0.1 ohms. What are acceptable ranges for each of those values?

There are five or six of the little peaking coils, all around that detector/video amp area. If I test them in circuit with an ohmmeter, I get either 4 or 7 ohms across them which are their values, does that sound like they are okay?


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sat 28, 2022 3:27 pm 
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Unless something caused too much current through them or are physically damaged I doubt a peaking coil is the problem.
The brightness of the CRT is controlled by the difference in the cathode and grid voltage, among other things. Check the voltage on the last video output plate, pin 6, it has a DC path to the CRT grid.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sun 29, 2022 12:57 am 
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frenchmarky wrote:
Will do, thanks.

I'm doing the resistance measurements of all the tube pins vs. the chart in the schematics also, never needed to try that before. Is there a rule of thumb as far as how close the readings need to be to the chart? Example, say three pins on the chart specify they should be 100K ohms, zero ohms and 0.1 ohms. What are acceptable ranges for each of those values?

There are five or six of the little peaking coils, all around that detector/video amp area. If I test them in circuit with an ohmmeter, I get either 4 or 7 ohms across them which are their values, does that sound like they are okay?


Absolutely, those coils are just fine. As for tolerances on those resistance measurements look at the associated components in the schematic, specifically any of the resistors associated with the pins and there tolerance. It looks like you changed over 3/4 of the resistors in the set when you rebuilt it. You replaced all of the caps, those maroon drops you used are usually good and rarely fail. Even used in modern circuits I have seen very few bad film capacitors. Resistance checks may point you in the right direction, I would start again from the detector forward, look for a GROSS resistance out of spec and investigate it. Example 100K and you read 120k, there could be a problem there. However voltage readings off G1, G2, K on the CRT and video output will tell the story. Also doesnt hurt to check the B+ and various other voltages listed off the voltages listed off the resistor divider networks in the power supply section. Remember many voltages will be a little higher than spec in the power supply because of higher line voltages but again here look for GROSS readings out of spec. A proper power supply is essential. Always use proper precaution on those high DC voltages and of course around an operating set.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sun 29, 2022 3:09 am 
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Looks like I changed roughly a third of the resistors. So if one pin measurement should be 0 ohms or 0.1 ohms, it's okay if it reads three or four ohms?


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sun 29, 2022 5:06 am 
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frenchmarky wrote:
Looks like I changed roughly a third of the resistors. So if one pin measurement should be 0 ohms or 0.1 ohms, it's okay if it reads three or four ohms?

Could be corrosion on the contact or resistance in your meter leads. Does your ohms zero out when shoring the leads together? And by corrosion I mean the thin layer of oxide present on tinned or plated contacts that causes a small amount of resistance. Also forms on solder joints over the years. Also make sure the ground is clean too when measuring to ground.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sun 29, 2022 6:48 am 
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Thank you, I'll check the meter and improve the connection between the meter and test point and ground point, and where I am connecting to ground and with what. How I have it set up now may be a bit iffy. Back to the tests!


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Sun 29, 2022 5:42 pm 
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In the power supply section of the schematic I see that there is a lower voltage B+ created from the main B+ by a voltage divider. That is: two resistors, one connected to the main B+ and the other to ground. There is an electrolytic cap bypassing that B+ to ground. If that electrolytic cap did not re-form correctly or the resistors are bad, that B+ could be low. Unfortunately the Sams does not show the B+ voltages, unusual for Sams. If your resistance measurements do not show anything you will have to then do voltage checks.

The voltage most directly affected by the lower B+ would be the plate (pin 6) of the second video amp.

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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Tue 31, 2022 6:33 am 
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Can you specify which resistors and cap you're talking about, I'll check it out.


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 Post subject: Re: Packard Bell - old recap job
PostPosted: May Tue 31, 2022 5:19 pm 
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frenchmarky wrote:
Can you specify which resistors and cap you're talking about, I'll check it out.

R103A, R103B & C3B.

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