Replacement part for 50yo bridge rectifier?

Stabby · 28th December 2010, 05:45 PM

I'm working on the pre-amp of a 50-year-old electric piano and will probably have to replace the bridge rectifier. It's pictured in this photo next to the transformer:

http://i.imgur.com/rH3KW.jpg

I have no idea what to look for though, since I can't interpret the information printed on the rectifier:

B250 075
KC068 22/8

Also, the rectifier is connected to two 350/395V capacitors.

Could anyone help me out?

nac134 · 28th December 2010, 06:16 PM

Google B250 rectifier. Theyre available.

Mooly · 28th December 2010, 06:20 PM

Hard to make out...
I assume it's silicon and not selenium... did selenium work at those voltages ?

You need to measure the AC voltage across the bridge and the DC across any reservoir cap. Does it follow the Vdc = 1.414 times Vac formula or not. Selenium has a larger volt drop. Just with you saying it was 50 years old.

Silicon... loads of choice but measure the voltages first and see what it runs at.

indianajo · 06:42 PM

You can replace selenium rectifiers with silicon, but sometimes you have to add series resistance at the appropriate wattage and voltage rating to keep the load voltage from getting too high. Note 1/4 W resistors are no longer rated at 400V because they are too short. 1 W resistors are usually rated above 400 V but check your supplier tables. Phenolic headers are handy for mounting discrete components to chassis at these high voltages, attaching to the metal with machine screws. tubesandmore.com sells them, calling them "terminal strips". I can't find headers at mouser, farnell, any of the usual international sources. With phenolic headers, you can also make a bridge out of 4 each 1n4007 etc. the way most vendors did in that era.

RJM1 · 08:41 AM

Are you sure it's not a B250 C75 bridge? If it is there is some information on replacing the B250 C75 selenium rectifer about two thirds down the page on this site:-

1958-1959 Grundig "2066 PX" AM/FM/SW Radio Restoration

You could use a small silicon bridge rectifier (about 1A 1000V) or four 1N4007 diodes in bridge formation, and a 100 ohm 10W resistor in series with the output to compensate for the voltage drop.

Mooly, 30KV Selenium diodes.
http://www.nteinc.com/specs/500to599/pdf/nte504.pdf

Mooly · 30th December 2010, 10:31 AM

Quote:

Originally Posted by RJM1

Mooly, 30KV Selenium diodes.
http://www.nteinc.com/specs/500to599/pdf/nte504.pdf

Thank you

28th December 2010, 05:45 PM	#1
Stabby diyAudio Member Join Date: Sep 2010	Replacement part for 50yo bridge rectifier? I'm working on the pre-amp of a 50-year-old electric piano and will probably have to replace the bridge rectifier. It's pictured in this photo next to the transformer: http://i.imgur.com/rH3KW.jpg I have no idea what to look for though, since I can't interpret the information printed on the rectifier: B250 075 KC068 22/8 Also, the rectifier is connected to two 350/395V capacitors. Could anyone help me out?

28th December 2010, 06:20 PM	#3
Mooly diyAudio Member Join Date: Sep 2007	Hard to make out... I assume it's silicon and not selenium... did selenium work at those voltages ? You need to measure the AC voltage across the bridge and the DC across any reservoir cap. Does it follow the Vdc = 1.414 times Vac formula or not. Selenium has a larger volt drop. Just with you saying it was 50 years old. Silicon... loads of choice but measure the voltages first and see what it runs at. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

28th December 2010, 06:37 PM	#4
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	You can replace selenium rectifiers with silicon, but sometimes you have to add series resistance at the appropriate wattage and voltage rating to keep the load voltage from getting too high. Note 1/4 W resistors are no longer rated at 400V because they are too short. 1 W resistors are usually rated above 400 V but check your supplier tables. Phenolic headers are handy for mounting discrete components to chassis at these high voltages, attaching to the metal with machine screws. tubesandmore.com sells them, calling them "terminal strips". I can't find headers at mouser, farnell, any of the usual international sources. With phenolic headers, you can also make a bridge out of 4 each 1n4007 etc. the way most vendors did in that era. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500 Last edited by indianajo; 28th December 2010 at 06:42 PM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
SCHOTTKY RECTIFIER FYP2010DN Y2010DN 20A/100V replacement/equivalent part help	steptoe1111	Parts	10	24th December 2010 07:59 AM
Bridge rectifier vs Full wave rectifier	hilbert_mostert	Tubes / Valves	4	28th April 2009 08:26 PM
Anybody heard about Tarzian Silicon Rectifier for Tube Rectifier Replacement?	zxx123	Tubes / Valves	4	21st February 2005 04:02 AM
Integrated Rectifier Bridge VS Rectifier Diodes	Sci	Chip Amps	11	16th July 2004 02:43 PM
Bridge Rectifier	thylantyr	Solid State	2	21st August 2003 09:11 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

28th December 2010, 06:16 PM	#2
nac134 diyAudio Member Join Date: Sep 2008	Google B250 rectifier. Theyre available.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read