Keysight MSO7034B, Teardown and Repair [Success]

[nctnico]

Hmm, normally replacement capacitors are smaller, not bigger!

[Samogon]

This new cap has an ESR of 0.07 Ohm
But only measures 298 uF
May be this one is better, because it has a larger volume.
But who knows, I have never used a Vishay electrolytic capacitor before.

Thank you all for help and suggestions, it is really appreciated.

It is still in 20% tolerance.
Again nice deal you made with this scope. Congratulations!

[Greybeard]

Can somebody help me to identify this diode in the front end of 7034A?
The font ends of 6034A and 5034A seem to be nearly identical to 7034A.

[mikeselectricstuff]

Can somebody help me to identify this diode in the front end of 7034A?
Is the font end of 7034A identical to 6034A and 5034A?

Unlikely to be anything exotic  - just measure the one in another channel  to determine how many diodes, shottky or not, zener or not.

[Greybeard]

Unlikely to be anything exotic  - just measure the one in another channel  to determine how many diodes, shottky or not, zener or not.

I don't like the idea of unsoldering one of the working ones, that would be the last resort.

[mikeselectricstuff]

Unlikely to be anything exotic  - just measure the one in another channel  to determine how many diodes, shottky or not, zener or not.

I don't like the idea of unsoldering one of the working ones, that would be the last resort.

At least you could try measuring it in-circuit

[HighVoltage]

I still have the original high resolution pictures and cropped this area out again
But it is still not readable.

I suggest like Mike said, try to measure the part in circuit and compare it to the other channels.
 

[mikeselectricstuff]

Would also be worth looking to see if there are parts with the same marking elsewhere ( apart from other channels) - if there are this would indicate that it's probably a fairly general-purpose device rather than something exotic

[Greybeard]

HV: I tried to process your photos, but no success.

Mike: BTW, awsome homepage (tesla photos).

[Greybeard]

Found a promising photo of the 1GHz frontend in this thread:
https://www.eevblog.com/forum/repair/agilent-dso6054a-noise-on-two-channels/msg853423/#msg853423




I think it is very probable same circuitry regarding this part:



So CR202/302/402/502 should be a double PIN diode HSMP3892 (HP/Agilent/Broadcom, marking code G2) = LXP1008‐23‐2 (Microsemi drop in equivilent).

https://www.digchip.com/datasheets/download_datasheet.php?id=384631&part-number=HSMP-3892
https://www.microsemi.com/document-portal/doc_download/9457-lxp1000-sot23-series-datasheet

PS:
Confirmed at 300MHz scope: Marking G25
Confirmed at 500MHz scope: Marking G2F
5 or F may be a maker or index mark.



PPS:
Case seems to be SOT-232 (smaller than SOT-23):




So correct diode type should be HSMP389C (same G2 SMD code):