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Old 26th Apr 2019, 7:07 am   #9
Diabolical Artificer
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Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,636
Default Re: Rectifier

Replace Bridge Rectifier as suggested above, any 400v 1A or above rated Bridge Rectifier will do or nick one out of a PC ATX PSU but check the datasheet first, the Bridge Rectifier's datasheet that is.

After the Bridge Rectifier between HT and + of the BR pop a big 5W low value resistor from your parts stash, 200 - 270r as suggested above or to start use a 100r. Clip your voltmeter leads either side of the resistor and switch the set on briefly but long enough for it to warm up. Divide the voltage reading by the resistor value to get the I or current, it should be around 100mA or below broadly speaking. From the schematic find out what HT should be then divide this figure by I (current) to get what value R you need, no need to get bang on as long as it's +/- 10v or so it'll be right.

Fit new R and then check HT is on spec. One other thing the schematic value will probably have been measured with an Avo or similar, so HT as measured with a DMM will be higher. Not sure if there is a rule of thumb to help figure the HT value as measured by a DMM, add 20v perhaps? Others here will know.

Andy.
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