开云体育

Mmm!?

Ok, so taking a closer look at the A5 board there are at least 4 IC's which have either been removed or 'attempted' to be removed.

Gonna have to pull these over the weekend, check or replace them and install sockets.

I'll be back...

On Fri, Feb 21, 2025 at 01:58 PM, <zheniak@...> wrote:

Indeed
/g/TekScopes/photo/300835/3889065?p=Created%2C%2C%2C20%2C2%2C0%2C0

While you are at it, you should check the resistor in series with the blown RIFA, current limiting NTCs for drift, and the resistors in parallel with the NTCs for damage.

There are three more RIFAs on the other board if it is similar to 2465B/2467B.
Ozan

So..

The reference voltages are both present. Perhaps 2 or 3 mV on the high side but very much present.

Indeed
/g/TekScopes/photo/300835/3889065?p=Created%2C%2C%2C20%2C2%2C0%2C0

I have found it's easier to loosen the collet holding the fan onto the
fan motor to do the removal. It can also be a good time to add some
silicone lubricant to the motor *if* it needs it.

On Fri, Feb 21, 2025 at 4:00?PM James55 via groups.io
<james_55@...> wrote:

Funnily enough I've removed and reinstalled several of these in the last couple of weeks.

My experience has shown me that there were two different types of fan used on these scopes. The earlier ones had the fan motor attached to the inverter board (with the two large filter caps) with a round fan protected by a metal plate, whilst the newer ones had a standard square-framed fan fixed to the rear of the scope.

The earlier ones need the fan removed first and then after removing a few screws on the rear panel, three from the lower heatsink, and disconnecting all the cables, it can be lifted straight up until the fan shaft nears the top of the rear hole, at which point the end facing the control panel needs to be angled and it easily lifts out.

The later ones just lift straight up and out (after screw and cable removal). They can feel like they're welded in but just make sure you keep it level and watch for the power cables getting in the way.

There are two Rifa's on the regulator board and three on the inverter board. All very straightforward to replace.

Good luck

Funnily enough I've removed and reinstalled several of these in the last couple of weeks.

My experience has shown me that there were two different types of fan used on these scopes. The earlier ones had the fan motor attached to the inverter board (with the two large filter caps) with a round fan protected by a metal plate, whilst the newer ones had a standard square-framed fan fixed to the rear of the scope.

The earlier ones need the fan removed first and then after removing a few screws on the rear panel, three from the lower heatsink, and disconnecting all the cables, it can be lifted straight up until the fan shaft nears the top of the rear hole, at which point the end facing the control panel needs to be angled and it easily lifts out.

The later ones just lift straight up and out (after screw and cable removal). They can feel like they're welded in but just make sure you keep it level and watch for the power cables getting in the way.

There are two Rifa's on the regulator board and three on the inverter board. All very straightforward to replace.

Good luck

Wow. That A/B Button trick is one worth remembering!...

The scope now has Scale Illumination and no longer goes to sleep.

..Still no trace, nor on-screen read-outs, but the relays can be heard clicking as I select different options.

Gonna look up where to find those -1.25 and 1.36 reference voltages

Roy, I have no idea if 10% resistors are still en vogue.
I have been fixing (or trying to fix) tube gear for some decades now, so there's plenty of that stuff in stock. And I'm sure I'm not the only one out here.

Regards, Joe

Not quite sure. They are visible without removing the board, and I don’t see any damage there. I’ll know better after removing A2."

The A2 and A3 boards can be removed by themselves and, I may be wrong about this, but I think loosening some of the screws on the back panel frees up a tab on one of those boards that slides into a hole the back panel.

Thanks,
Barry - N4BUQ

Thank you Ozan!
I just got the manual. Indeed, there are instructions on how to do it.
Z.M.

Aren't the likely Rifa suspects (C1016 and C1018) on the A2 board?

Thanks,
Barry - N4BUQ

On Fri, Feb 21, 2025 at 09:40 AM, <zheniak@...> wrote:

My main question is: Can I remove the A2 and A3 boards without taking out the
A1 (Main Interface) board first?

Service manual section 6-25 describes how to remove A2 and A3, it doesn't need removal of A1. If the construction is similar to 2465B I found that removing IEC power supply filter made access easier. I don't know if 2465 has the same filter.
Ozan

Could be DC restorer diodes or something else in the blanking circuit.
Ozan

Thanks for your quick response, I will start looking into that area.

Craig

On Fri, Feb 21, 2025 at 09:43 AM, Craig Cramb wrote:

Looking into a 465 S/N B260137 and trying to determine what seems to be
causing the additional trace in background of triggered wave forms. Power
supplies all look good for voltage and ripple. Suspecting trigger board but
exactly unsure. Any thoughts would be welcome
Added photos to album : 465 Scope with Ghost trace

Most likely blanking is not working, you are seeing the trace travel back from end of sweep (right side) to beginning of sweep which should have been blanked. Since retrace happens faster than the regular sweep it looks like a slower waveform. Could be DC restorer diodes or something else in the blanking circuit.
Ozan

Looking into a 465 S/N B260137 and trying to determine what seems to be causing the additional trace in background of triggered wave forms. Power supplies all look good for voltage and ripple. Suspecting trigger board but exactly unsure. Any thoughts would be welcome
Added photos to album : 465 Scope with Ghost trace

Craig

Thanks in advance.

The squished horizontal is due to low voltage on the 8.6V--in fact all the DC voltages are low by about 15%.
(I have read all the 2235 power supply problems and got the schematics in large format.)
I have extensively probed the power section before the CRT HV section.

i have replaced some caps.
When i unplug Q9070 the voltages are fine so i am looking in the section the follows the mosfet-bottom of the schematic and Q908.
VR943 is flaky and it is connected to Q944 which the table says is a SI NPN 625MW, TO-92, Manu part # is TO7391E2-this is a pretty general description!
Before i replace the VR943 i want to check Q944.
i (think) equivalents may be MPSA42, MPSA55, MPSA14, BC337, BC547B.

Can anyone definitively state the proper equivalent?

Hi everyone,

Yesterday, while working with my Tektronix 2465, I suddenly heard a strange noise from inside, followed by a very unpleasant smell. There was no smoke, and the trace was still visible on the screen. I immediately turned it off and haven’t tried powering it on since.

I suspect it might be a Rifa capacitor gone bad, but I need to inspect the boards to be sure. After removing the cover, I realized that I can’t clearly see how to remove the A2 (Horizontal) and A3 (Vertical) boards.

My main question is: Can I remove the A2 and A3 boards without taking out the A1 (Main Interface) board first?
Or is there another trick to access them more easily?

Any tips or advice from those familiar with the 2465 would be greatly appreciated!

Thanks in advance!

On Fri, Feb 21, 2025 at 05:03 AM, Gianni Becattini wrote:

Provided I check the value, could I use normal resistors even if they are not
specific for high voltage?

You could... and some designs do.. but they use a series string of them to reduce the voltage across each one.
The current is common to all... and the power dissipation of each resistor should be factored in.
See the resistor's data sheet, for the 'maximum working voltage."

--
Roy Thistle