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By "buzzing out" I mean using a meter with either a buzzer /continuity or set to ohms to find what wire goes where. The intensity pot wiper - white/yellow stripe wire I think - goes from the front of the scope, to the back/EHT section. It connects to R830, a 3M3 resistor & some caps, the other end of R830 goes to the grid of the CRT. So, find R830 by tracing the wiring, once confirmed pop your meter across it set to DC volts, power on, read meter.

If you have a cathode/grid short you'll get a high reading, over a 10v say. A normal valve correctly biased has a grid current of a few uV if so, that which would give a reading of 6v ish. I could be wrong about this though, others please chip in & tell me if I'm wrong.

Andy.

Mike this is exactly what I just said.

On Mon, May 26, 2025 at 9:30?PM Mike Drum via groups.io
<mjdrum1958@...> wrote:

New Rifa caps have the same failure mode as old Rifa caps???

I sure hope that's not true! Does anyone know for sure. Hard to imagine
manufacturing steps have not been taken to eliminate that.

Mike

On Mon, May 26, 2025, 20:52 Mr. Fang via groups.io <thomas.fang=
[email protected]> wrote:

I had to purchase this value (.1uF + 22ohm) recently for a Tek 7912AD
repair, and if it helps anyone, the part number to order at Mouser is
80-PMR209MC6100M022. (Assuming you're ok with the risk of newer RIFA caps
having the same failure mode as old ones.)

-Thomas

New Rifa caps have the same failure mode as old Rifa caps???

I sure hope that's not true! Does anyone know for sure. Hard to imagine
manufacturing steps have not been taken to eliminate that.

Mike

On Mon, May 26, 2025, 20:52 Mr. Fang via groups.io <thomas.fang=
[email protected]> wrote:

I had to purchase this value (.1uF + 22ohm) recently for a Tek 7912AD
repair, and if it helps anyone, the part number to order at Mouser is
80-PMR209MC6100M022. (Assuming you're ok with the risk of newer RIFA caps
having the same failure mode as old ones.)

-Thomas

I had to purchase this value (.1uF + 22ohm) recently for a Tek 7912AD repair, and if it helps anyone, the part number to order at Mouser is 80-PMR209MC6100M022. (Assuming you're ok with the risk of newer RIFA caps having the same failure mode as old ones.)

-Thomas

Thanks Mark. Will contact my friend to see if he has the appropriate adapter.

Gordon

Thanks Andy, but a bit puzzled by your procedure. My DMM doesn't have a continuity beeper so not sure what you mean by "buzzing out" from the intensity pot. Are we trying to determine if the resistance across R830 changes when the intensity pot is rotated? Or are we looking for an excessive voltage drop (>1V?) across it when the scope is (presumably) powered on.

Thanks
Gordon

According to a later manual the change was made at B040000:
0.1uF + 22 ohm 250VAC
Albert

Bruce your on 240 or 120V mains?

THe 240V blows them often!

120V no so.

Jon

My advise is this: Look up the RIFA parts you are replacing and then
use parametric search to find another vendor. RIFAs problem isn't wear
out from heating & cooling or "dry out". I left a fresh order of them
in their original packaging in a box in a climate controlled closet
(away from UV light) for a few years and when I opened it the
encapsulation had cracked. I believe the resin mix used is going
through an overly aggressive cure to keep the production line running
fast or something.


On Sun, May 25, 2025 at 6:54?PM bandrsn via groups.io
<bandrsn@...> wrote:

All,
Well, it finally happened - POP! - sizzle, sizzle. My fine 7104 blew its RIFA capacitor in a loud manner, and I know, I should have replaced it sooner.

I found what's left of the RIFA in the shielded power supply, but there's not enough of it left to get info from its case.
The downloaded service manual and schematics don't exactly match the B053423 S/N. The A23 Inverter Board shows two ceramic 0.02UF, 1400VDCAC capacitors in parallel (C1205 and C1206), both in series with a 27 Ohm resistor, R1205. My A23 board has (had) a single RIFA where R1205 was and what appears to be a jumper across one of the places for the capacitors.
My question is, what should the replacement RIFA be? Since the exploded one is in bits and pieces I can't get enough info from it to know.
The schematic shows the RIFA directly across the hot and neutral lines after the power switch.

Any brand/device values, etc. recommendations for a commonly available 115VAC replacement that, hopefully, will not explode again?

Also, the power supply construction makes it difficult to gain access to the back side of the Inverter Board. I was able to carefully snip away the bits of the RIFA plastic and foil, etc. so there are about 1/4" or slightly more of the tinned leads sticking out on the component side. I was planning to cut, bend and quickly solder to these exposed leads, being careful not to melt the solder too much on the other side and cause a short.

Does anyone foresee a problem with this if care is also taken to avoid any shorts, etc. on the component side too?

Thanks,
Bruce
AB6BA

Bruce,

If you want .047mfd:
If you want .068mfd:

The value is not critical. The latter is common in the 2000 series as mains filters. What I sent is X1 type that is higher voltage rating than X2. You can use a resistor where the original was which is in series with the filter.

Getting to the underside of the bottom board is not that difficult. There are four small phillips screws that hold the bracket for the two main screw cans. Two are on the rectifier/regulator board and four are on the side panel with the vent holes. Remove the two filter cans making sure to get polarity right when reinstalling. You can put in an additional NTC off the mains while you are in the cavity. A CL-70 is an option.

If you have not already done so, clean out the odor and any deposits left by the exploding condenser.

Mark

They are usually 47nF+47R or 100nF+100R or 47nF+100R. I use all three indiscriminately according to availability. I can’t see that it matters much.

All,
Well, it finally happened - POP! - sizzle, sizzle. My fine 7104 blew its RIFA capacitor in a loud manner, and I know, I should have replaced it sooner.

I found what's left of the RIFA in the shielded power supply, but there's not enough of it left to get info from its case.
The downloaded service manual and schematics don't exactly match the B053423 S/N. The A23 Inverter Board shows two ceramic 0.02UF, 1400VDCAC capacitors in parallel (C1205 and C1206), both in series with a 27 Ohm resistor, R1205. My A23 board has (had) a single RIFA where R1205 was and what appears to be a jumper across one of the places for the capacitors.
My question is, what should the replacement RIFA be? Since the exploded one is in bits and pieces I can't get enough info from it to know.
The schematic shows the RIFA directly across the hot and neutral lines after the power switch.

Any brand/device values, etc. recommendations for a commonly available 115VAC replacement that, hopefully, will not explode again?

Also, the power supply construction makes it difficult to gain access to the back side of the Inverter Board. I was able to carefully snip away the bits of the RIFA plastic and foil, etc. so there are about 1/4" or slightly more of the tinned leads sticking out on the component side. I was planning to cut, bend and quickly solder to these exposed leads, being careful not to melt the solder too much on the other side and cause a short.

Does anyone foresee a problem with this if care is also taken to avoid any shorts, etc. on the component side too?

Thanks,
Bruce
AB6BA

Hakan,

After knowing about the socket problem, is it best as PM to do a sweep of the sockets in the scopes and plugins? Is there a point where the sockets were better so replacing would not be needed? If so, what year? There are 8 and 16 pin sockets that will have this problem. I have seen some of the sockets have contacts that make contact on the sides of the IC pins. These will have small holes where the pins go in. Some dual wipe sockets that are taller to give more contact surface area work well. The MilMax machined types are better by being machined. Is the machined type the preferred type to use?

Mark

On Thu, May 22, 2025 at 11:12 PM, Rogerio O wrote:

Also, I intend to reseat (with some Deoxit) all the IC's and connectors of the readout board.

While you are at it check if they are the bad TI C95 sockets. They are trouble waiting to happen.
Some spray might help but probably only for a short time.

/H?kan

That worked, thx. After cold start (with J156 removed), self cal and ext cal the scope returned with 0 Fail messages.

Finally solved! I replaced the battery, that did not clear all the Fail messages but then I forced a cold start (after J156 removed).
Then a 'self cal' and an 'ext cal' (the latter needed to apply some voltages to the 2 inputs and a fast rising signal), and all Fail messages were finally cleared.
Thx to you all for giving me the direction to get this solved. I love my 2343A scope and I would hate to miss it.

On May 22, 2025, at 14:12 , Rogerio O via groups.io <rodd414@...> wrote:

I was thinkin to start with the easiest issue (2) which would require spraying a little of Deoxit Fader on the pot's wiper but, to my surprise, it seems impossible to get there
see (/g/TekScopes/album?id=302608).

I'd try taking the knobs off and spraying Faderlube down the shaft before disassembling it, and I'd also try that from the exterior and see if it'll wick through any gaps.

For garbage and missing values in readout, don't forget your vertical and horizontal plugins. I've had more problems with those causing missing/wrong readout due to dirty/damaged cam switch contacts. YMMV.

Adam

Roger,

You may have to, unsolder the leads from the diodes from the rear wafer, loosen the nuts on the rear of the switch enough to keep them on, loosen the nut for the pot, move the pot back enough to get access to the tabs holding the metal case on, pry the tabs back enough to get a gap where you can spray cleaner inside then reverse to get back to original. It is possible you will have to remove enough to get the pot out to clean it. I know it is a lot of work. Drilling a hole will get metal shavings inside the pot. I had two pots that were open in a Bogen DB130 I had to replace the guts. That had a similar thing as you have, a wafer and wires that needed to be removed. This has concentric controls. It took a few hours in my case. No other way was possible.

Mark

Thank you very much for having time to check and post this reply, Barry
Roger

Hello and need help for this part.
I’m looking for the vfd display used in the counter timer of the 2236.
Part number is 670-7423-01 for the small board and 150-1110-00 for just the display tube. The display tube also known as a
Noritake Itron p/n FG94C1.