Solved. 05-30-2020 Hameg Model HM203-6 Oscilloscope that is not working - Page 1
Forum section: electronics / repair

author: kastell123
author_rank: Contributor
timestamp: May 25, 2020, 07:26:16 am
content: I have a Hameg Model HM203-6 Oscilloscope that is not workingDeformed (not straight) amplifier horizontal line (Y) is seen this in oscilloscope mode and in equal components mode, (not line) correct, I upload images to see.Please help.Thank you.

author: kastell123
author_rank: Contributor
timestamp: May 25, 2020, 07:42:08 am
content: I have a Hameg Model HM203-6 Oscilloscope that is not workingDeformed (not straight) amplifier horizontal line (Y) is seen this in oscilloscope mode and in equal components mode, (not line) correct, I upload images to see.Please help.Thank you.

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 25, 2020, 10:07:22 am
content: Start by checking power supply voltages and ripple, this looks like interaction between X and Y (X deviation influencing Y) that should not normally happen.Is it dynamic only or static and dynamic? If you set spot to center position in XY mode then shift it to left or right edge with position control or external DC input does it also move up or down?Is there interaction the other way round? Does modulating the Y axis in XY mode also cause X axis movement?Considering your sweep amplitude looks reduced I'd definitely start with checking power.

author: kastell123
author_rank: Contributor
timestamp: May 25, 2020, 05:55:19 pm
content: Thanks for the answer, tomorrow 05-26-2020 I confirm your questions.I think that the point, axes (Y) (X) if I can move them?Just add for your information, that this breakdown suddenly occurred, one day I left it working fine (OK), and another day when I went to use it, was the breakdown present?

author: kastell123
author_rank: Contributor
timestamp: May 25, 2020, 06:19:29 pm
content: Thanks for the answer, tomorrow 05/26/2020 I confirm your questions.I think, by pressing the button that cancels deflection the point, axes (Y) (X) if I can move themI can tell you for your information, that this fault, happened suddenly, one day I left it working fine (OK), and another day when I went to use it, it appeared, with the fault.Sorry for my expressions, it's for the google translationI understand something of the English language, but a little.

author: kastell123
author_rank: Contributor
timestamp: May 26, 2020, 08:46:30 pm
content: HelloI have uploaded a video to Youtube for better fault compression.Please open the link below.Thank you.

author: shakalnokturn
author_rank: Super Contributor
timestamp: May 28, 2020, 06:36:11 pm
content: Have you checked all power supply voltages?

author: kastell123
author_rank: Contributor
timestamp: May 29, 2020, 07:50:05 am
content: If all voltages ok except the voltage (-12) which are (-16.84 v)

author: firewalker
author_rank: Super Contributor
timestamp: May 29, 2020, 08:08:22 am
content: I had a similar problem with my HM-604. It was a faulty bridge rectifier on the power supply. AC was passing through the bridge and was creating issues like yours.Alexander.

author: kastell123
author_rank: Contributor
timestamp: May 29, 2020, 08:18:53 am
content: All voltages ok except voltage (-12) which are (-16.84v)Power source, to bien except (-16.84) in brand scheme (-12 v)Sorry there are some, voltages on circuits with errors.In the final horizontal amplifier (X Final Amplifier) in the channel that attacks the deviation plate (D1) there is + 99 v, and in (D2) + 131, obviously there is an error, the two voltages must be almost the same with some difference of 2… 5 volts No (32 volts) it seems that there is no consumption on the board (D2) or I have some pre-amp before the final amplifier, with defect (some Bf199) the Bf458 and BF472 checked and well, I will continue investigating 1 (-16.84) and check BF199.Why doesn't the point appear when I press the (X-Y) button… ??

author: kastell123
author_rank: Contributor
timestamp: May 29, 2020, 08:25:43 am
content: Thanks, AlexanderI'll check that bridge, rectifier.

author: kastell123
author_rank: Contributor
timestamp: May 30, 2020, 03:44:46 pm
content: Solved. 05-30-2020The whole problem was because of this cross capacitor(c714 0.1UF (100K 63V) (short, total) now there is (- 12 volts)Before (-16.84 volts) this was the whole problem, just this shorted capacitor, nothing else.Attached diagram for clarity of the affected component.This afternoon I will upload 2 videos, to see the solution.

author: kastell123
author_rank: Contributor
timestamp: May 30, 2020, 09:01:46 pm
content: Elace condensador culpable de averia.Solucionado 30-05-2020

author: jdragoset
author_rank: Frequent Contributor
timestamp: May 31, 2020, 12:29:08 am
content: Great "sticking to it" work.Got a way-to-cheap Tek 067-0532-00 Constant Amplitude Calibration Fixture ( with GR 1363 unit oscillator to 500 megahertz)Q707 (SCR) was missing but could momentarily short A to K and start the unit.Saw above 100 mhz sine wave but shortly vanished with smoke/heat around the 40 uf, 500 volt dual-section Mallory electrolytic. Got a dual section, 50-uf, 500 volt replacement for under $20Same size and the original poly sleeve actually fit.Adding an NTE 5410 SCR would still not start but found Q 711 (SCR gate quench) shorted.Replaced with a 2N5961 and all works.Off subject but never give up!