HELP with Selenium Rectifier Replacement - Wurlitzer 1700

I'm rebuilding the 524HF tube amp on my Wurlitzer 1700. What is the
correct value for a Silicon Rectifier Replacement for the 524HF?

I was looking at 35amp bridge rectifiers ...

http://www.web-tronics.com/semicondu...ectifiers.html

Is there anything wrong with over-specification of the rectifier? I'm
leaning towards the 35amp, 1000V model.

If anyone has links to a specific URL that deals with replacement of
selenium rectifiers with modern silicon rectifiers, that would be
helpful too.

No problem with replacing a Selenium with a silicon - just make sure
the fuse is between the transformer and the AC input for the bridge as
silicon bridges short whereas selenium fail open. The silicon will
burn out your transformer if it ever shorts with no fuse in line....

John :-#)#

On 2 Jun 2004 15:20:26 -0700, (Fred) wrote:

I'm rebuilding the 524HF tube amp on my Wurlitzer 1700. What is the
correct value for a Silicon Rectifier Replacement for the 524HF?

I was looking at 35amp bridge rectifiers ...

http://www.web-tronics.com/semicondu...ectifiers.html

Is there anything wrong with over-specification of the rectifier? I'm
leaning towards the 35amp, 1000V model.

If anyone has links to a specific URL that deals with replacement of
selenium rectifiers with modern silicon rectifiers, that would be
helpful too.

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

There is nothing wrong with over specification. In this case by about a
factor of 100, but with silicon as cheap as it is, who cares?

There is one technical problem you need to address. There will be less loss
or voltage drop across the silicon diodes than the seleniums, raising the B+
significantly. This may overstress some parts of the circuit. A series
resistor should be added between the output of the bridge and the input of
the filter. Use ohm's law to determine the resistance necessary to drop the
B+ voltage to approximately the original value, and don't forget the power
dissipation E x I = W, which will likely be on the order of several watts.
Use an appropriately sized power resistor.

--
Crazy George
Remove N O and S P A M imbedded in return address
"Fred" wrote in message
om...
I'm rebuilding the 524HF tube amp on my Wurlitzer 1700. What is the
correct value for a Silicon Rectifier Replacement for the 524HF?

I was looking at 35amp bridge rectifiers ...


http://www.web-tronics.com/semicondu...-amp-bridge-re
ctifiers.html

Is there anything wrong with over-specification of the rectifier? I'm
leaning towards the 35amp, 1000V model.

If anyone has links to a specific URL that deals with replacement of
selenium rectifiers with modern silicon rectifiers, that would be
helpful too.

As I remember, the selenium rectifier is used to provide power to the record
changer (carousel) drive motor; it's mounted on the amp chassis simply as a
matter of convenience, and has no electrical connection to the amp circuitry.
Thus there's no reason to worry about a different voltage drop.

Joseph "Tony" Dziedzic

In article , "Crazy George"
wrote:
There is nothing wrong with over specification. In this case by about a
factor of 100, but with silicon as cheap as it is, who cares?

There is one technical problem you need to address. There will be less loss
or voltage drop across the silicon diodes than the seleniums, raising the B+
significantly. This may overstress some parts of the circuit. A series
resistor should be added between the output of the bridge and the input of
the filter. Use ohm's law to determine the resistance necessary to drop the
B+ voltage to approximately the original value, and don't forget the power
dissipation E x I = W, which will likely be on the order of several watts.
Use an appropriately sized power resistor.

On 2 Jun 2004 15:20:26 -0700, (Fred) wrote:

I'm rebuilding the 524HF tube amp on my Wurlitzer 1700. What is the
correct value for a Silicon Rectifier Replacement for the 524HF?

I was looking at 35amp bridge rectifiers ...

http://www.web-tronics.com/semicondu...ectifiers.html

Is there anything wrong with over-specification of the rectifier? I'm
leaning towards the 35amp, 1000V model.

There's nothing wrong with overspecifying apart from wasting money. A
1A 400V part would probably do the job just as well, would be tiny,
and would cost about 20 cents. It's your money though :-)

As others have said, fit a suitable fuze if there isn't one already -
not to do this is a false economy.

Best regards, Paul
--
Paul Sherwin Consulting http://paulsherwin.co.uk

In article pQDvc.44733$Ly.4135@attbi_s01,
(Joseph A. "Tony" Dziedzic) wrote:

Thus there's no reason to worry about a different voltage drop.

Ok ok ok, that's true 99% of the time, but just to be pendantic, you
*do* have to watch the cycle speed on some machines. Generally, most
mechs with DC motors run at about 24-28V DC, which is where the selenium
would have it. The sillicons are a bit better, so they'll have the
voltage up a bit higher. This *can*, but doesn't always, cause the
machine to run a bit on the fast side. I know on my AMI F, it's enough
to get the mech to fling the tonearm at the record as opposed to
lowering it nicely.

A resistor in the appropriate changer motor circuit would be better than
one big dropper after the rectifier - you'll still get the nice crisp
selections, but the change speed will be dropped enough to avoid killing
records..