Alignment Tools?
- Thread starter super98lsc
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super98lsc
Well-Known Member
HP 5328A option 010, has A3 oscillator support board for 10MHz oven oscillator 10544A. If does not have the oven option, it a standard crystal osc, with no temp stabilization.
Options are printed on labels placed on the back. You have option 030, channel "C" 5-512MHz, 15mV sensitivity.
This model was our factory cal standard at Motorola back in '85
Too bad about the 2445. Scopes are fun to fix, need a scope to fix a scope
Good news is I have a reconditioned/mint condition 2246 100MHz Tek scope that although its a lower model # its FAR nicer and more options features than the 2445. And I snagged that Type 191 because its supposedly good for fixing/calibrating scopes.
However since I have never repaired a scope before.... any pointers on where to start.
Mine will fire up and give all the measurements / settings on screen. The CRT isnt too terrible but compared to my professionally rebuilt 2246 its no comparison.
This pic is not mine but notice how this one shows 4 horizontal lines... mine only displays the cursors.
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2445, just more troubleshooting skills, I would need a service manual before even trying to fix it or offer any advise where the problem lies.
Type 191, sure makes sense, scope cal unit for gain flatness, b/w testing. We used to have another one, forget the model, it was used for cal/verify analog scopes, had markers/sweep time settings, so you could cal/check the horz sweep time settings, just line up the markers with the vertical graticules. I loved my job at the Motorola cal/test lab, I learnt so much about test equipment and systems. Recall having over 2000 pieces of gear logged in and accounted for. Some were fun to fix, took days, more than one tech to figure out the issue. Do not recall ever having to give up and send back to the mfg to sort out and charge a small fortune.
When I left Motorola, '87 they gave me a parting gift of a old HP 400D VTVM, collectors item.
I was reading and thinking about the IG-37 again. I think you use the marker output and tune the radio to them, say the ones at the band ends. When you are off tune, you get RF noise detected. Of course muting is off. When you tune to a marker, it quiets the radio. So on one end, hi-end you adjust the RF coils for maximum quieting, then tune to the lowest marker, adjust the cap trimmers for maximum quieting. Go back and forth a few times to even out. You can tune to the other markers in the middle, to fine tune, probably adjust the fins on the var cap for linearity.
Give it a try.
Type 191, sure makes sense, scope cal unit for gain flatness, b/w testing. We used to have another one, forget the model, it was used for cal/verify analog scopes, had markers/sweep time settings, so you could cal/check the horz sweep time settings, just line up the markers with the vertical graticules. I loved my job at the Motorola cal/test lab, I learnt so much about test equipment and systems. Recall having over 2000 pieces of gear logged in and accounted for. Some were fun to fix, took days, more than one tech to figure out the issue. Do not recall ever having to give up and send back to the mfg to sort out and charge a small fortune.
When I left Motorola, '87 they gave me a parting gift of a old HP 400D VTVM, collectors item.
I was reading and thinking about the IG-37 again. I think you use the marker output and tune the radio to them, say the ones at the band ends. When you are off tune, you get RF noise detected. Of course muting is off. When you tune to a marker, it quiets the radio. So on one end, hi-end you adjust the RF coils for maximum quieting, then tune to the lowest marker, adjust the cap trimmers for maximum quieting. Go back and forth a few times to even out. You can tune to the other markers in the middle, to fine tune, probably adjust the fins on the var cap for linearity.
Give it a try.
super98lsc
Well-Known Member
That does makes sense. I too was reading that in the manual last night. Ill need to test a few more things out with it tonight. Spent last night cleaning up the lab and adding in the new toys to the racks.
On the scope I read that the U800 chip is a bugger to find and prone to heat failure. From what I can gather though none of the displays would work at all if it were dead? Not certain yet. All the voltages/ms sec/div etc along with the horizontal cursors display fine. Just no traces. Beam find works fine.
On the scope I read that the U800 chip is a bugger to find and prone to heat failure. From what I can gather though none of the displays would work at all if it were dead? Not certain yet. All the voltages/ms sec/div etc along with the horizontal cursors display fine. Just no traces. Beam find works fine.
super98lsc
Well-Known Member
IG-37 certainly has an issue.
The Oscillator is not functioning properly. Following the post assembly calibration instructions, at the 2nd step the procedure is to adjust the Oscilator voltage. Well mine has zero effect. I do have a 60hz sine (these oscillate at line rate) but the problem is it has 20v peak to peak and 9.8v RMS which should not be anything above 2v.
The manual states it could be caused by either or both of the 2 12AU7 tubes in that portion of the circuit V1 or V5. All the tubes light up fine and get warm no red plating or anything abnormal. However I do not own a tube tester
The Oscillator is not functioning properly. Following the post assembly calibration instructions, at the 2nd step the procedure is to adjust the Oscilator voltage. Well mine has zero effect. I do have a 60hz sine (these oscillate at line rate) but the problem is it has 20v peak to peak and 9.8v RMS which should not be anything above 2v.
The manual states it could be caused by either or both of the 2 12AU7 tubes in that portion of the circuit V1 or V5. All the tubes light up fine and get warm no red plating or anything abnormal. However I do not own a tube tester
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super98lsc
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The schematic I have someone penciled in 63v at R620. I cannot find "A" on my schematic...I could be going blind though. Have a lead on R62.
EDIT:
I just found it was staring right at it ... ugh...
EDIT:
I just found it was staring right at it ... ugh...
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super98lsc
Well-Known Member
Measures 114 vDC
AC measured only 154mV
If the writing on the schematic is correct then i have near 2x the voltage I should have.
I noticed 3 times now that the front power light would just go out on its own. I waited for that failure mode and started tapping components. Funny enough when I tapped the metal can Mult-Cap (same test points were talking about) the front panel lamp popped right back up. Even though all the caps tested OK on my Agilent LCR I did not pull the multi can cap out of the circuit to test it.
AC measured only 154mV
If the writing on the schematic is correct then i have near 2x the voltage I should have.
I noticed 3 times now that the front power light would just go out on its own. I waited for that failure mode and started tapping components. Funny enough when I tapped the metal can Mult-Cap (same test points were talking about) the front panel lamp popped right back up. Even though all the caps tested OK on my Agilent LCR I did not pull the multi can cap out of the circuit to test it.
super98lsc
Well-Known Member
Ok I pulled the Multi Cap can.
114uf (spec is 100uf) ESR .389 ohms
44.38uf (spec is 40uf) ESR . 934 ohms
38.45uf (spec is 40uf) ESR .836 ohms
Diode checks good
2w resistor is 360 ohms (spec is 330ohms)
1/2w resistor is 877ohms (spec is 820)
114uf (spec is 100uf) ESR .389 ohms
44.38uf (spec is 40uf) ESR . 934 ohms
38.45uf (spec is 40uf) ESR .836 ohms
Diode checks good
2w resistor is 360 ohms (spec is 330ohms)
1/2w resistor is 877ohms (spec is 820)
Voltages at "A" sound about right! What do they measure on the other side of R62, should be higher DC and more ACV as well.
The NE2H neon pilot light is on its way out. I assume it is a 90V breakdown neon lamp. Should be easy to find.
Then I am guessing tarnished contacts. it is always good to remove tubes from sockets, re-seat them, in and out a few times to wipe tarnish/oxide from contact points.
Measure V1-b pins 2,3 for a sine wave, if not try swapping V1 with V2(V3) and try again. Hard to imagine 3 of 12Au7 being bad at the same time. Check the bias voltages on all the V1,2 pins and report them. Bias on V1A is the same as V5, so that is something to compare against. It should not be too hard to fix.
Lots of other things to check, 19KHz osc, 38KHz doubler, 100MHz osc, markers, see what works and what does not.
Have fun
Rick
The NE2H neon pilot light is on its way out. I assume it is a 90V breakdown neon lamp. Should be easy to find.
Then I am guessing tarnished contacts. it is always good to remove tubes from sockets, re-seat them, in and out a few times to wipe tarnish/oxide from contact points.
Measure V1-b pins 2,3 for a sine wave, if not try swapping V1 with V2(V3) and try again. Hard to imagine 3 of 12Au7 being bad at the same time. Check the bias voltages on all the V1,2 pins and report them. Bias on V1A is the same as V5, so that is something to compare against. It should not be too hard to fix.
Lots of other things to check, 19KHz osc, 38KHz doubler, 100MHz osc, markers, see what works and what does not.
Have fun
Rick
super98lsc
Well-Known Member
Rick thank you very much for the help on this. Here is what I know works thus far.
I will snag the voltages off all the pins tonight and post them up. Thanks again for the help. Figure this re-introduction to tubes will help refresh my brain before I get into this Thordason Amp I have on the shelf waiting for attention.
- I know the 100MHz works because I can tune a receiver to 100Mhz and pickup the IG-37 and use the fine tune on the IG-37 to center the 100MHz +/- 2MHz.
- While the receiver is tuned to 100MHz I can broadcast a signal through the IG-37 to the receiver via the composite input on the IG-37 using an external source generator or PC.
- The 19kHz works I was able to dial that in on step one of the tuning and watch / measure the frequency on both my 2246 scope (with cursors) and the Freq Counter. Also was able to lock the amplitude down to 3v or less per the instructions by adjusting the coil.
- At one point I observed nothing but 60Hz hum out of one of the features but do not recall which connection I was connected to.
- I tried swapping around the tubes. There is an 12AU7 that is not part of the Audio OSC circuit and it made no change. I agree it would be odd for all 3 to be bad. And I know V3 works because that function works.
I will snag the voltages off all the pins tonight and post them up. Thanks again for the help. Figure this re-introduction to tubes will help refresh my brain before I get into this Thordason Amp I have on the shelf waiting for attention.
super98lsc
Well-Known Member
Funny you mention that lamp I removed and Ohm'd it out and put it back in the 1st day before ever powering it up. I thought that lamp was only to glow/light up in case of an issue or short. At least in the instructions so it says. It serves another purpose? I'll replace it to be certain
Do not replace the bulb unless you have same exact one. Here it is used as nonlinear device to stabilize oscillations. It is a part of circuit like other resistors and capacitors, and needs to have very specific parameters to work correctly.
further, the lamp acts to provide agc action to stabilize the osc level, since it has a positive temperature coefficient, as the osc level increases, the filament heats up the resistance increases, thus the gain decreases (nfb action), similar as to what HP did with the old 200CD VTube oscillator. Other,newer methods are to use a jfet or a LDR, modulated by the coupling of a light from a LED in a sealed unit. Know one uses the filament technique anymore, as it is very prone to microphonics.
See
http://www.edn.com/electronics-news/4389675/Low-distortion-oscillator-tests-measurement-circuits
http://www.edn.com/design/analog/4368298/Test-18-bit-ADCs-with-an-ultrapure-sine-wave-oscillator
Does not sound like it is a lamp issue, so it can only be a few other possibilities.
So where is the 60Hz coming from?, it must be a open circuit somewhere, lots of gain, picking up hum.
See
http://www.edn.com/electronics-news/4389675/Low-distortion-oscillator-tests-measurement-circuits
http://www.edn.com/design/analog/4368298/Test-18-bit-ADCs-with-an-ultrapure-sine-wave-oscillator
Does not sound like it is a lamp issue, so it can only be a few other possibilities.
So where is the 60Hz coming from?, it must be a open circuit somewhere, lots of gain, picking up hum.
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super98lsc
Well-Known Member
Ordered all new tubes today for giggles. They should arrive in the next day or 2.
I will remove and retest the lamp it had a certain level of resistance but I have not ever illuminated it to see if its fully functional.
The 60Hz supposedly is where this unit gets its oscillation freq from but certainly should not be part of the test signal outputs rofl. I will go through it more tonight and post updates.
I will remove and retest the lamp it had a certain level of resistance but I have not ever illuminated it to see if its fully functional.
The 60Hz supposedly is where this unit gets its oscillation freq from but certainly should not be part of the test signal outputs rofl. I will go through it more tonight and post updates.
"The 60Hz supposedly is where this unit gets its oscillation freq from"
and what part of the circuit does this?
I am looking at T1, where is the tap off point? secondary side, so that it gets injected into the audio path through to the composite amp V5A
I would not apply 120VAC to test the lamp, unless you have a spare one, maybe powering with a variac or a phase cut dimmer, set to min for starters, with something this old, the last thing you need is shock treatment. I never had to change a lamp in a 200CD, it was usually tubes, 6CW?? Look for ecaps too, how about C4(40u/150V) remove V1, test C3 var cap, might be able to get the wiper in between so to remove the R's in the circuit. make before break switch? or make break make, type?
and what part of the circuit does this?
I am looking at T1, where is the tap off point? secondary side, so that it gets injected into the audio path through to the composite amp V5A
I would not apply 120VAC to test the lamp, unless you have a spare one, maybe powering with a variac or a phase cut dimmer, set to min for starters, with something this old, the last thing you need is shock treatment.
I never had to change a lamp in a 200CD, it was usually tubes, 6CW?? Look for ecaps too, how about C4(40u/150V) remove V1, test C3 var cap, might be able to get the wiper in between so to remove the R's in the circuit. make before break switch? or make break make, type?
super98lsc
Well-Known Member
Im not certain where in the manual I read that about the 60Hz. Tried to find it now and cannot.
This is what I found on the neon front panel lamp. (I know were talking about the other bulb inside).
From the manual "The neon lamp indicates the presence of B+ voltage and is used as a pilot lamp."
My question is what does "used as a pilot lamp" mean?
I use shock treatment to fix my thoughts... rofl
This is what I found on the neon front panel lamp. (I know were talking about the other bulb inside).
From the manual "The neon lamp indicates the presence of B+ voltage and is used as a pilot lamp."
My question is what does "used as a pilot lamp" mean?
I use shock treatment to fix my thoughts... rofl