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Re: RG501 Ramp Generator running at double speed?
On Wed, Dec 29, 2021 at 07:15 PM, David C. Partridge wrote:
The dial is just a potentiometer, no steps on this one. The manual says it is only calibrated on the '1' position, and all other positions are uncalibrated, it does go up to 11 though, but I guess you'd have to measure the output while dialing it in during use. There's no indication that the dial should be rotated respective to the potentiometer, and when I tried it, I lost adjustment at the top of the dial's range. |
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Re: RG501 Ramp Generator running at double speed?
Is it simply the knob being off by one position on the shaft (or are is it 1-2-5?)?
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-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Jared Cabot via groups.io Sent: 29 December 2021 07:34 To: [email protected] Subject: Re: [TekScopes] RG501 Ramp Generator running at double speed? I have it set to internal trigger but the output discrepancy is the same when triggered from my TG501A Time Mark Generator. If I set the Time Mark Generator to 0.1us and the Ramp Generator to 1us, I don't see the expected 10 time marks per one ramp, which is what initially alerted me to this fault. I re-set the relevant trimpots to half scale and ran through the ranges with the front dial set to '1' and output amplitude to max (output should be 10V P-P) Range - Output - Output Amplitude 10us - 5.7us - 4.4V 100us - 30.6us - 3.2V 1ms - 250us - 2.7V 10ms - 1.8ms - 2.1V 100ms - 24.6ms - 2.7V 1s - 163ms - 1.9V I checked all the voltages into the Sweep Control and Miller Integrator, and they seem to agree with the schematic. Also the front panel Gate Output coincides perfectly with the ramp output, which comes straight from the Sweep Control chip via a couple transistors. |
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Re: RG501 Ramp Generator running at double speed?
I have it set to internal trigger but the output discrepancy is the same when triggered from my TG501A Time Mark Generator.
If I set the Time Mark Generator to 0.1us and the Ramp Generator to 1us, I don't see the expected 10 time marks per one ramp, which is what initially alerted me to this fault. I re-set the relevant trimpots to half scale and ran through the ranges with the front dial set to '1' and output amplitude to max (output should be 10V P-P) Range - Output - Output Amplitude 10us - 5.7us - 4.4V 100us - 30.6us - 3.2V 1ms - 250us - 2.7V 10ms - 1.8ms - 2.1V 100ms - 24.6ms - 2.7V 1s - 163ms - 1.9V I checked all the voltages into the Sweep Control and Miller Integrator, and they seem to agree with the schematic. Also the front panel Gate Output coincides perfectly with the ramp output, which comes straight from the Sweep Control chip via a couple transistors. |
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RG501 Ramp Generator running at double speed?
Hi,
I am currently repairing an RG501 Ramp Generator and have found it seems to be running at double speed, that is, when I set it to 1ms, it produces ramps of 500us width, this double speed is true for all ranges. I have set the relevant adjustment pots to center range and it's sitting squarely at this double speed, and the trimpots don't have enough adjustment to correct the issue. So far, I've checked the voltage rails, all are spot-on. I've replaced the couple carbon composite resistors (all out of tolerance) with metal film, cleaned all the push button switches, and replaced the Sweep Control and Miller integrator IC's with brand new parts (U30 155-0056-00, and U50 155-0042-03 respectively) as they were faulty. It seems to work fine now, besides the double speed pulses.... Here's the schematic for reference: Can someone give me some pointers of where to poke? I can't find much data on the Sweep Control IC around. Thanks! |
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Re: Tek 465B graticule lights
On Tue, Dec 28, 2021 at 08:12 AM, Joe wrote:
Refer to Schematic #12 POWER SUPPLY. The entire circuit is laid out there and this will help guide you. NOTE: I am referencing Manual # 070-2757-00. Other manuals may be slightly different Confirm no voltage change at the pins for P4086 on the A4 board when rotating the scale illumination control. Of course, check the lamps to make sure they are still good Check F4507 for an open condition. If F4507 is not open, check + terminal of C4531 for About 9V. Check +5V (Unreg) and +15V LV supplies for correct voltage at the various test points and circuit components. You need a minimum of +5V (Unreg) and +15V for scale illumination to work. IF your LV is in good order, then check the individual Scale illumination circuit components Q4190, R4193, R4195 and VR4194 (7.5V Zener). Q4190 is a Darlington transistor, test accordingly. If you supply the correct voltages to the circuit, there is not much else that can go wrong. -- Michael Lynch Dardanelle, AR |
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Re: Update: Re: Help with 7D15 Tek logic gates
Thanks, good point Jim.
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I'm not completely familiar with this circuit nor MECL implementation details yet. I don't think there's a Vtt in this design, but there are occasional Rs to Gnd on the same circuits as open emitter Rs. There is a variety of open emitter R values as well. I can't make rhyme or reason of them. I didn't pay attention to the reading on the DMM, I was just using the "beep mode" continuity check. It could well be the many parallel Rs on the Vee. The beep will activate even with appreciable resistance in circuit. I'll recheck that today while I clean up the board in prep for reassembly. Dave On Tuesday, December 28, 2021, 12:16:28 AM PST, Jim Ford <james.ford@...> wrote:
Say, Dave, the Vee to Gnd shorted thing may be unrelated, but I will bring up the Vtt appearing to be shorted to Gnd issue anyway.? Saw it first back in the late 1980s when I first worked with ECL.? Vtt is the voltage that the 50 ohm terminations connect to, usually -2 V.? All the 50 ohm terminations on the board, each in series with the output impedance of its driving gate, about a few tens of ohms, are effectively in parallel.? Could read as low as a few ohms or less and look like a short.? Just a thought.? ?HTH.? ? Jim FordSent from my T-Mobile 4G LTE Device -------- Original message --------From: "Dave Peterson via groups.io" <davidpinsf@...> Date: 12/28/21? 12:00 AM? (GMT-08:00) To: [email protected] Subject: [TekScopes] Update: Re: Help with 7D15 Tek logic gates Incredulous would be the word that comes to mind when I think how I felt about my diagnosis of U287C being dead in this 7D15. But I could not reason why else I was getting no signal out on pin 14. Stuck HI (0.7v) IIRC.I really didn't believe that the issue was U287C specifically. With U287C suspect I couldn't say anything about U287D, but U287A and B appeared to be working if I recall my testing results. Would a single instance of a quad just fail? There was nothing physically questionable about this part, and well isolated from inputs to have been overloaded.After waiting to procure a proper desoldering station to remove the MECL 1662 NOR quad pack from the A6 Interface Board, I finally got the little bugger out this morning.I had also purchased a couple of NOS 1662s online. I did a little study, then set up a breadboard test bench, and after working through a few snafus I was able to prove that indeed, U287C alone is non-functional in this package. All three other NORs are working, and all four of one of the replacements are as well.Thanks for the inputs. The feedback has gone a long way to bringing me up to speed on ECL logic in Tek parts.I have some board clean up to do from the removal process, and I think I may have measured a short from Vee to Gnd. Shorted Tant? Maybe. Don't hold me to that yet. Careful testing and reassembly shall ensue. I won't call it fixed until I can have it in a scope and running some counts.I'll post an update if/when fixed.Dave |
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Tek 465B graticule lights
I have a Tek 465B that had a graticule bulb burn out. I replaced the bulbs, but must have sparked the board to the chassis when replacing it as I have no voltage at the output now.
I¡¯m currently looking through the manual now, but if anyone has any input I¡¯d greatly appreciate it! |
Jared Cabot
David C. Partridge
Michael W. Lynch
Dave Peterson
Joe