Fluke 8050A 220V mod

[Neshco]

In the circuit diagram the +13 V voltage is used for the main amplifiers and for 2 V input, some 5 V drop at the FETs and some 2 V for the drain side resistors a voltage of 8 V should be sufficient for that circuit part to work. It is a bit strange that the plan also gives +13 v and -10 V from the same rectifier, just the other half.

The filter capacitors are only 220 µF - this is normally only good for some 100 mA at best, especially if the raw votlage without regulation is also used.. So I would not expect the meter to take much power.
The battery circuit looks like it would charge the battery with some 130 mA / 200 mA (if the regulator is a LM317).  It is not so clear if the charge time is with the meter on or off, thus the 2 currents.
This would mean cells of some 1.3 or 2 Ah, which would be sub C of C size about which would sound reasonable. For a 10 hour run time this would be some 130 or 250 mA at some 5 V (4 cells in series). So this would be some 0.6 or 1.2 W as power drawn from the batteries. This could much more reasonable. With a +-10 V supply this would be some 50 mA per side which about fits for 220 µF filter capacitor. This would still result in some 2 V of ripple, which is well on the high side to power parts of a sensitive circuit.

So a 4 or 5 VA transformer should be OK, even 3.2 VA may work, but could be close as the transformer would provide a slightly higher voltage and because of filtering would need some 1.4 VA per watt.

The question is if even a 9 V transformer may be enough, at least least with 220 V mains, maybe not all the way down to 200 V as the original fluke specs.

The input power specs include the loss of the transformer, while the rating is for the output. The small transformers usually have a relatively poor efficiency, like mybe 70% if they were good.


For getting tranformers there may be a better, more local source than Ali- express. They are just a bit heavy for shipping.
A European alternative would be this:  https://www.tme.eu/en/details/ts4_30/transformers-with-fastening/indel/ts-4-30/

Thank you for this, just, pay attention that this is the model without batteries. Schematic cover both versions, guess you get battery one. Batteryless version have tap on the middle while Battery version does not, just two wires on the secondary side. Then, guess, this transformer would be fine? And thank you for the shop, didnt know that it is there, just to check if shipping prices are not kidney expensive.

[Neshco]

For getting tranformers there may be a better, more local source than Ali- express. They are just a bit heavy for shipping.
A European alternative would be this:  https://www.tme.eu/en/details/ts4_30/transformers-with-fastening/indel/ts-4-30/

Just to confirm that this transformer is installed and work nice. Thank you Kleinstein!
I have not tested it yet thoroughly because I plan to replace the electrolytic capacitors and clean it, but so far it look just fine. No obvious problems.

Off topic:
Mechanic switches was worked very poor on this device, often did not lock etc. I have clean it with the contact cleaner and now there is no any problem it switch nice and lock everytime, just clicking sound is somehow strong and sharp, not sure it is normal, there must be some kind of grease there.
Is there some dielectric greasing spray that can be used here to get smooth movement and sound when switching, to grease it?