Fluke 8840A's with similar problems.

[Paceguy]

I have two Fluke 8840A's with similar problems:

1st one: Powers on, display works. Once I go thru the self test, the keypad becomes unresponsive, none of the keys work remains on DC range and measures DC voltages. The self test shows no errors. If I power down and turn it on again, it won't do the self test. If I power it down and wait for a hour or two, I can get it to self test but right after that the keypad becomes unresponsive again.

I have tried swapping out U212, issue remains. Could it be U203 or U208? Power supply voltages are all dead on.

2nd one: Powers on, display blank, can hear relays click when range and function keys are pushed, the 6 keys on the right side, ( rate, trig, offset, SRQ) appear unresponsive no relay clicking heard when pressed.

I switched out U212 and U202. No change. Power supply voltages are good. Could it be U203 or U208?

Any advice would be much appreciated. Yes, I have a scope, and Pace desoldering equipment. I have repaired other 8840/8842A's but it's the first time that I run into these problems. Thanks in advance.

[Slh]

Are the power supply voltages dead on before and after the self test that makes the first one unresponsive? When mine was playing up something in U301/U302 or U303 (can't remember off top of my head but it's in my posts) was latching up when cold and drawing too much current but not when hotnso sometimes the voltages were dead on.

[J-R]

Quick question: did you already reflow the transformer connections?

[Paceguy]

Quick question: did you already reflow the transformer connections?

Yes, reflowed the transformed connections.

[Paceguy]

Are the power supply voltages dead on before and after the self test that makes the first one unresponsive? When mine was playing up something in U301/U302 or U303 (can't remember off top of my head but it's in my posts) was latching up when cold and drawing too much current but not when hotnso sometimes the voltages were dead on.

I will check the voltages in both conditions. Thanks.