Bosch Oven HBC84E653b/04 cutting out after 30 secs – no capacitor to discharge??

[johnboy183]

I have seen several posts on this microwave oven where the timer functions for 30 secs with no apparent heating then defaults back to 1min. The conventional part of the oven works. The fault appears to be either the Magnetron or the Inverter board from what I have read. However on trying to follow standard advice to make the oven safe to work on I cant find (on the exploded diagrams) any sign of a high voltage capacitor to discharge to render the circuit safe. Do these Invertor models not have such a high voltage capacitor or is it on the Invertor board or elsewhere? Any help will be gratefully received as have no wish to have my remaining hair stand on end through 5000 volts!.
John

[electrofix]

the inverter does not need a cap as the cap in the conventional circuit act as a voltage doubler but you still have to discharge it just in case

try this

if you look at the mag there are often small holes in the top box

if you turn the lights down and look through these holes while its running you may see a glow of the heater

if you see a glow chances are its just the mag

for any other member of the public reading this microwaves contain lethal voltages and should not be played with unless you know what your doing

Dave

[johnboy183]

Hi Dave,
Thanks for the very quick reply.
Are the caps in the “conventional circuit” those on the Invertor board? (see photo) Are any of these 5000volt capability of do invertor models not have these very high voltage caps?
Exploring what you asked me to try do you mean to have the outer case off and activate the microwave while looking through the holes in the mag to look for a glow? (see other photo) – and is this safe?
John

[johnboy183]

Hi Dave,
Tested the magnetron in situ and it seemed to test out as ok using the various Multimeter tests. However for completeness I decided to remove it for a full inspection and found the damage shown in the attached photos! Hopefully the Magnetron replacement will effect a cure unless there are other unforeseen issues. Would welcome your views?
john

[kaibart]

Change the magnetron and all will be fine

[electrofix]

you can get the mag off ebay a lot cheaper than from Bosch as the system Bosch use is made by panasonic

you will have to hope the inverter is ok unless you test it

the caps on the inverter can still hold a charge and have to be discharged but in the old system the cap is bigger and therfore is more likely to kill you if not discharged

Dave

[johnboy183]

Thanks both.
managed to order a brand new identical and genuine mag from eBay for £47 delivered – far cheaper than from bosch!
I can’t see any obvious burnt or blown caps or components on the inverter board so shall see if the mag replacement fixes the problem and if not I will delve deeper. ( the oven is some 10 years old and the microwave has been used a lot so hopefully just a worn out magnetron). I will report back later and hope the outcome also helps others. John

[kaibart]

Advise the customer that 900w power is not for re heating food they must use 600w for a longer period that is more than likely the reason magnetron has failed

[johnboy183]

Sorry for the delay in updating this post but have been away for a couple of weeks and have only just installed the Magnetron (Im sure that was the name of a death ray in Captain Scarlet and the Mysterons way back )
Anyway it would appear that the burnt out Mag was indeed the problem as machine now fully working again.
Kaibart – I have indeed strongly advised the “customer” (my wife!) of what you have said which as you might imagine went down very well as these pieces of advice do!!
Thanks again everyone for your invaluable advice and help as always.
kind regards
John

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