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Hello

I am at a standstill with figuring out why the CRT of my 2465A is blurry and won't focus.

I purchased this unit from Government Planet last summer with the idea that I would probably have to troubleshoot it. I turned it on and it made a screeching sound and had no display. I thought the sound was coming from the fan but no it was the high voltage board. Checked the voltages on J119 and they were all good with the exception of the -15V rail which had high ripple. Decided to recap the LVPS with a kit from Condor Audio. This fixed the -15V rail. Turned it on and there was a blurry dispay but intermittent screeching from the high voltage board. Looked closer at this and discovered that the ceramic of T1970 was cracked in several places. Purchased a new high voltage board from QService and installed it. Now no screeching but the display remains blurry with the Read Out letters wider and taller than they should be and the same for the traces. I have uploaded 2 pictures to the file Amberwave 2465a that shows what I'm talking about. I checked voltages to the CRT socket at pins 8(31V), 12(-108V to -186V) and 13(-192V to -224V) and they look reasonable. DAC reference is right at 10V. When I input a signal into the scope I can just make out that it is a sign wave.

I just don't know where to go from here. I have invested a lot of time and dollars in this scope to just give up. It would seem that this isn't a HV board issue as both boards gave a blurry image. Could this be the CRT tube itself or one of the IC's? I would really appreciate some guidance on where to go from here from someone more experienced with these scopes than me

Rusty Hilliard
W0RGH

Bonjour WORGH, have used,and fixed 2465/7/B since 1990s.


I am very wary of any older SN, or no suffex 2465 or A.

Any vendor with "government" is also a flag.

Repair can be PS, or HV, and control board,A5 CAL,RAM, SMD,lytic corrosion

CRT damage is rare, unless it,was dropped or mispackaed in shipment

The very,severe defects appears more,than a PS, or just bad HV.

Even for very experienced 2465 veterans, with best CAL equipment, it can take hours, days weeks...

One,dog I have had on the bench since 2018!

You should get the full service manual for the model and serial, follow the excellent flow charts and check each board and subassembly in sequence

Alternatively just write it off as,a parts,donor, and look out for a,100% working 2465B.

Bon courage


Jon

Rusty,

R1853, R1854, R1871, R1872 and R1880 are known problems. Replace them with 1W 1% types. When any of these go bad, focus will not work. R1991 should be replaced with a Vishay or Ohmite type.

Mark

Mark
Many thanks! This is the kind of information I need. Will put the order in with Mouser tomorrow.
Rusty

Rusty,

The 150,000 ohm: 71-CCF60-150K-E3, 180,000 ohm: 279-H4P180KFDA, 332,000 ohm: 71-CCF60-332K-E3, 442,000 ohm: 71-CMF60442K00FEWF (12 week delay) or (2) 660-MF1/2CC2213F (in series), 430,000 ohm: 279-H4P430KFZA, 100meg: 708-HVA12FA100M or (measure in mm the hole spacing of the original carbon then select the on that will drop in which will be larger in wattage than original). If yours has the two 39meg 1/4w carbons on the bottom board, use two 594-MBE04140C2005FC1 in series. These will be R710 and R910.

Mark

Mark

So the HV board that is in the scope now is not the original but rather a "new" board from QService. I had hoped this would be a known good board. Perhaps that is not the case. The original board had a cracked HV transformer. Do you feel strongly that I should start replacing resistors on this "new" board?

I have the luxury of being able to compare resistance values across both of the HV boards that I have albeit this testing is in-circuit and with one of the boards installed into the scope (connected to power supplies, etc.). My measurements are similar between the 2 boards.

My A1 board does have the carbons for R710 and R910. Both test about 2.3k in-circuit. Do you have a 2465A and could test some of the resistances across these resistors? Don't get me wrong. I can start swapping out resistors but would hope there is a decent likelihood of that solving the problem.

This is not what is seen with an IC failure right?

Any point to checking more voltages at the CRT socket?

Rusty