|
Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
|
Thread Tools |
8th Jul 2020, 5:23 pm | #1 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,884
|
Replacing a Westinghouse bridge rectifier
Hi there
I'm repairing an old Ekco record player (RP329) which uses a transformer and bridge rectifier. The original recifier was giving only half voltage so I've replaced it with a modern bridge. However the HT is a bit too high (285v against 228v in the manual) and the ECL 82s are getting a tad too warm for my liking. Should I include a dropper resistor in series with the HT line? All the usual capacitors have been replaced, of course. |
8th Jul 2020, 5:40 pm | #2 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,549
|
Re: Replacing a Westinghouse bridge rectifier
Yes you can place a resistor in series with the DC output. Or you can put a resistor in each leg of the AC feed to the rec. Values found by experimentation or alternatively use ohms law to work out what resistor you need in the HT line to drop the 57 volts at the appropriate current. Rough guess I'd start at 100 ohms or thereabouts.
__________________
There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
8th Jul 2020, 5:42 pm | #3 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Replacing a Westinghouse bridge rectifier
It's standard practice to include a resistor of 200R or so in the HT line when doing this, which replicates the behaviour of the metal rectifier more accurately and gives the smoothing caps an easier life. Some people adjust the resistor so that the HT voltage is absolutely spot on the service data voltage, but it isn't really necessary.
|
8th Jul 2020, 6:36 pm | #4 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,884
|
Re: Replacing a Westinghouse bridge rectifier
Thanks - that's what I thought. Luckily there's plenty of room on the chassis to fit a large wirewound.
|
8th Jul 2020, 6:46 pm | #5 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Replacing a Westinghouse bridge rectifier
5W is usually OK, even 3W at a pinch.
|
9th Jul 2020, 4:04 pm | #6 |
Dekatron
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 6,884
|
Re: Replacing a Westinghouse bridge rectifier
Thanks - in the end a 330 ohm did the trick as the amplifier isn't very power hungry. It's just a two-valve unit using two ECL82s as pre-amp, phase splitter and push-pull output stage. Not going to blow your socks off or win hi-fi awards, but nice to see a push-pull circuit in an ordinary record player.
|
9th Jul 2020, 4:30 pm | #7 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
|
Re: Replacing a Westinghouse bridge rectifier
It would have been a good performer compared with many record players of this era. Nice to see that it will be back in use again.
__________________
Frank |
9th Jul 2020, 5:39 pm | #8 | |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
|
Re: Replacing a Westinghouse bridge rectifier
Quote:
With the correct anode voltage, two ECL82s in PP will offer 6-8 watts. I would regard that as pretty pokey for the average living room....
__________________
Edward. |
|
9th Jul 2020, 6:48 pm | #9 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
|
Re: Replacing a Westinghouse bridge rectifier
Yes, not a bad spec for a mono portable record player.
|