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Thanks Jon, I have a DS1225 on order from Mouser. When you say 'use EEPROM programming to load default CAL' what do you mean - is there some default binary for the NVRAM?

As regards the triggering issue, I have already replaced all PSU caps and verified the voltages. The A5 board SMU caps aren't leaky and measure OK too. I'm wondering if it could be an issue with U500? I may be able to lay my hands on one of those.

cheers

Keith

Ah sorry Victor, when I wrote that I had not noticed the SM caps on A5.
They do look OK - no leakage - and measure OK in circuit as far as I can tell. But they probably should be replaced.

Keith

So I desoldered the DS1225 nvram carefully and fitted a 28 pin DIL socket.
Took the nvram and just to see if there was still any life in it I programmed it using a TL866ii programmer, using a .bin file from the EEVblog thread.

With the nvram replaced, the scope booted up without any errors. Now this was just a temporary test until I get a known good DS1225AD from Mouser, but at least it proves that the original cal data was bad ;) And the readout does not have the question marks anymore, hurray.

The remaining issue is the triggering. The symptoms are:
- scope triggers in auto lvl / auto mode with sweep speeds longer than 2mS. At 1mS it triggers most of the time, but not all, with faster timebase speed it gets more and more intermittent and at 500uS or so it stops triggering. This is with Y input at 200mV/cm and probe on the cal point (400mV p/p).
- the display is OK, everything reading as expected there.

Before I start going through sweep troubleshooting, has anyone seen a trigger issue like this?

Keith

Hello Keith,
I also have trigger problems with my 2465B. The SRAM Dallas has already been replaced and refilled because of the old Li battery. Because the Scope also had (and still has) the error message "TEST 05 FAIL 42" I had the board 05 examined by a Tek professional - without success. Visually, I cannot detect any corroded or burned components.

Greetings JuHe

Keith bravo for your work on NV Ram, beware of Chinese knock-off and old date code parts.

Use machine pin socket

Full cal is needed after RAM replacement

See service manual and proper test equipment

Can be hours or days first time.

Trigger issues described may be marginal trigger hybrid U400, or symptoms of damaged A5 control board due to SMD lytic corrosion

Beware of hidden damages in A5 visa, parts or inner layers.

Corrosive liquid and gas of the SMD lytic flow over the board, even if caps look OK

Tell tale is dull, green pads or joints, near the DAC ref area on A5, controls jumpy or intermittent

Every SMD lytic needs replacement.

Every nearby component and trace is suspected

Bon chance

Jon

Merci Jean-Paul

Probing the TGA signal from pin 18 of U500, the triggering waveform there is as I see it on the screen i.e. intermittent. So it looks like U500 or circuitry before it in the trigger path is faulty.Time to read the theory of operation of the trigger circuitry I guess.

Something is borderline as triggering is OK at slow sweep speeds but not at < 1ms/cm.

Keith

Rebonjour

Does the trigger issue, affect all 4 ch and line or only certain channels?

Trigger path is from vert amps and multiplex IC.

Use the self test, one og the tests or exer is for trigger.

See trigger debug flow chart in service manual

Bon chance

Jon

It affects all channels in the same way. Hence the thought that it's maybe an issue with U500?

Keith

Well, whaddya know. I found this while randomly searching for 2465B problems:



The description of the triggering problem was identical to the one I have... and sure enough, removing the J102 plug made the problem go away. The scope now triggers perfectly. The author of the above article never persued the fix any further, so I might just look into why the TV sync option is causing a problem on my 2465B.

- Keith