Fluke DSP-4100 and DSP-4300 Repairing

[NinjaPirate]

Hi All,

I have been trying to figure out a problem with my Fluke DSP-4100 network tester and am getting nowhere so am after some guidance on where i should be focusing (I'm not the most skilled with electronics repair but have done soldering/ basic voltage testing etc.)

I have a DSP-4100 Smart Remote that no longer powers up, when turning the dial to on you hear a slight buzz noise but no leds light up. I have tried additional batteries known to be good from the main unit but still the same 'error'. As the main unit has recently come up with an internal battery error I measured the internal batteries on both the main unit and smart remote, both were low so i ordered up some replacements and soldered in - still no dice on the smart remote but the main unit is now happy.

I have then brought a couple of DSP-4300 Smart remotes from eBay thinking i could do some part swaps or just use one of those instead, turns out you cannot use a DSP-4300 remote with a DSP-4100 main unit, unless someone knows a way?
I have tried swapping the top control board (the dial section), didn't make any difference. I tried changing the middle board, still nothing. Oddly if i plug a charger into the non-working unit with any of these boards replaced the slight buzz seems to repeat as if the unit is trying to start. If i plug a battery into the unit and apply the charger is does seem to charge the battery.

I read through a great post on the forum about a DSP200 which helped me with the internal battery replacement but as it is for a different unit doesn't give much additional help on what else i could try. I am guessing the ROM chip has gone bad but no idea how i go about replacing that or even if i did how i would program it again?

Any assistance would be gratefully appreciated, my knowledge is a bit exhausted but i am willing to learn  It's been a trusty little tester and i would hate to part with it so anything i can do to bring it back into service!

[lunar]

For starters, you need to understand basic electronics troubleshooting. 1. Check the voltage rails. 2. Check that the main micro powers up and has a clock signal. 3. Look for some activity on the micro data lines.

Youtube has an endless amount (more than a lifetime's worth) of electronics troubleshooting videos. Start with some Signal Path videos, and maybe some Learn Electronics Repair or EEVblog repair videos, and that will give you some idea of what you are getting into.

If you want to troubleshoot here, post some pictures of the boards, and at least start by showing the voltage rails are operational. An oscilloscope is preferred, but you can post pictures of a DVM if that's all you have. Look for any blown components. What do you think the failure mode of the network tester was?

There is a very likely chance that you won't be able to fix it, so don't get your hopes up too much.