Electronics > Repair
ZT–702S Multimeter/Oscilloscope Reading Pulsed 6.3 V heater supplies!
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Chris56000:
. . .I'm providing technical assistance down at a local Retro Arcade near where I live, and I'm currently having difficulty with one of those Zotek ZT–702S not reading the pulsed 6.3 V CRT heater supply on C.R.T. arcade game display chassis – it detects the frequency as "15.84 kHz" but the voltage shown is negligible!

. . .Have I got a faulty instrument or has it got such a poor frequency response that the so–called "true–r.m.s." converter can't read it?

. . .Will the ZT–703S read this type of supply in Multimeter Mode?

Chris Williams
abeyer:
The specs say: Frequency response of ACV: 40Hz-1kHz

https://zotektools.com/products/zoyi-zt-703s/
Chris56000:
. . .It can't be a very good so–called "true–rms" converter in it, my UT61E is only quoted up to 1 kHz in the leaflet I got with it, but the UT61E can read that type of supply – I took it down there today and tried it on one of their C.R.T. displays and read back 6.1 V!

. . .The Arcade Staff would buy me a suitable meter if they're not horrendously expensive – can anybody suggest anything quoted up to 15 kHz or better – or would I be better with an analogue True RMS Meter for these supplies?

Chris Williams
Xena E:
I assume the heater being a winding on the sweep transformer: the 15*** kHz would indicate that.

To accurately measure the heater power it can be compared with a suitable hot wire or thermionic measuring instrument.

If niether are available, compare the emission of a suitable indirectly heated valve between being powered from 6.3 volts DC and the HF source, this will be best measured by comparing the current in short circuit between the cathode and first grid.

Most meters won't make any sense of the hf frequency or waveform from the sweep transformer.

X
timop:
I would recommend the Brymen BM869s DMM. The AC+DC true rms bandwidth is 100kHz, and the inputs are rated CAT IV/1000V. IMHO it's a reliable and robust meter that provides a lot of features and good accuracy for the price.
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