I have seen the solid state replacement using the octal base for the
tube. I have a Hammarlund HQ 145XC that uses it, and it runs hot after
an hour or so. Just wondering if anyone else has used this replacement.
I found it for $9.99 on Tubedepot.com.
Thanks

On 7/14/2012 3:20 PM, Bob Grimes wrote:
I have seen the solid state replacement using the octal base for the
tube. I have a Hammarlund HQ 145XC that uses it, and it runs hot after
an hour or so. Just wondering if anyone else has used this replacement.
I found it for $9.99 on Tubedepot.com.
Thanks

Hi,

I looked at the solid-state plug in ad, but it appears
that it doesn't include a series resistor to drop the voltage
downstream to the same value as when the original 5U4 is used.
If it did, the solid state rectifier plug-in itself would run very hot.

I suggest you add a 200 Ohm 20W wirewound resistor
between pin 2 of the 5U4 tube socket and the input
to the HV filter choke/first electrolytic.
(Hammarlund might have used pin 8 for this purpose, also,
but the schematic shows pin 2).

The 5U4GB drops about 50V at its max rated current, 275mA,
per the tube data books, compared to less than a volt
for the plug-in replacement. That's why the external resistor
is required.

73,
Ed Knobloch

I've never used a purchased solid state replacement, but in days of old many
of us tried
a do-it-yourself replacement. Most had good results. I didn't. I don't
recall using a dropping
resistor as Ed suggests, but it sounds ok. What I had problems with was the
solid state
diodes I was using had a much sharper cut-off (reverse current cut-off) that
generated
a little RF hash that interfered with weak signal reception. There were
others that experienced
the same thing. I was not alone. My RME 4350 ran hot, alright, but propping
open the hinged
access door on top helped a lot. Ed, what did others do to stop the sharp
cut-off hash?

Old Chief Lynn


"Bob Grimes" wrote in message
...
I have seen the solid state replacement using the octal base for the
tube. I have a Hammarlund HQ 145XC that uses it, and it runs hot after
an hour or so. Just wondering if anyone else has used this replacement.
I found it for $9.99 on Tubedepot.com.
Thanks

On 7/15/2012 1:15 AM, coffelt2 wrote:
I've never used a purchased solid state replacement, but in days of old
many of us tried
a do-it-yourself replacement. Most had good results. I didn't. I don't
recall using a dropping
resistor as Ed suggests, but it sounds ok. What I had problems with was
the solid state
diodes I was using had a much sharper cut-off (reverse current cut-off)
that generated
a little RF hash that interfered with weak signal reception. There were
others that experienced
the same thing. I was not alone. My RME 4350 ran hot, alright, but
propping open the hinged
access door on top helped a lot. Ed, what did others do to stop the
sharp cut-off hash?

Old Chief Lynn


Hi, Chief

In case of increased hash with the solid-state rectifier
replacement, I'd add two .01 disc ceramic capacitors
to the 5U4 socket, across pins 4 and 2
and 6 and 2. The capacitors should be rated at 2 KV.

73,
Ed

On Sun, 15 Jul 2012 11:15:27 -0400, Edward Knobloch wrote:

On 7/15/2012 1:15 AM, coffelt2 wrote:
I've never used a purchased solid state replacement, but in days of old
many of us tried a do-it-yourself replacement. Most had good results. I
didn't. I don't recall using a dropping resistor as Ed suggests, but it
sounds ok. What I had problems with was the solid state diodes I was
using had a much sharper cut-off (reverse current cut-off)
that generated a little RF hash that interfered with weak signal
reception. There were others that experienced the same thing. I was not
alone. My RME 4350 ran hot, alright, but propping open the hinged
access door on top helped a lot. Ed, what did others do to stop the
sharp cut-off hash?

Old Chief Lynn


Hi, Chief

In case of increased hash with the solid-state rectifier replacement,
I'd add two .01 disc ceramic capacitors to the 5U4 socket, across pins 4
and 2 and 6 and 2. The capacitors should be rated at 2 KV.

73,
Ed

Thanks for all the good advice. It seems like I would just be better off
keeping the tube! I knew that guys on this group would come through with
the solution.

On Mon, 16 Jul 2012, Bob Grimes wrote:

On Sun, 15 Jul 2012 11:15:27 -0400, Edward Knobloch wrote:

On 7/15/2012 1:15 AM, coffelt2 wrote:
I've never used a purchased solid state replacement, but in days of old
many of us tried a do-it-yourself replacement. Most had good results. I
didn't. I don't recall using a dropping resistor as Ed suggests, but it
sounds ok. What I had problems with was the solid state diodes I was
using had a much sharper cut-off (reverse current cut-off)
that generated a little RF hash that interfered with weak signal
reception. There were others that experienced the same thing. I was not
alone. My RME 4350 ran hot, alright, but propping open the hinged
access door on top helped a lot. Ed, what did others do to stop the
sharp cut-off hash?

Old Chief Lynn


Hi, Chief

In case of increased hash with the solid-state rectifier replacement,
I'd add two .01 disc ceramic capacitors to the 5U4 socket, across pins 4
and 2 and 6 and 2. The capacitors should be rated at 2 KV.

73,
Ed

Thanks for all the good advice. It seems like I would just be better off
keeping the tube! I knew that guys on this group would come through with
the solution.

The solid state replacement doesn't use filament power, so the load on the
transformer is less.

Michael VE2BVW

Michael Black VE2BVW wrote:
The solid state replacement doesn't use filament power, so the load on
the transformer is less.

Yes, and will result in 15 Watts less heat in the cabinet
with the 5U4 gone. Stability will be improved
and warm-up time reduced. Just don't forget
to add the 200 Ohm resistor to bring the B+ back to normal.

73,
Ed Knobloch

Bob Grimes wrote:
I have seen the solid state replacement using the octal base for the
tube. I have a Hammarlund HQ 145XC that uses it, and it runs hot after
an hour or so. Just wondering if anyone else has used this replacement.
I found it for $9.99 on Tubedepot.com.

What's in it? Is it just a pair of 1N4007s, or does it also have a power
resistor?

If you replace a tube rectifier with a pair of solid state ones, your B+
voltage will rise. How much? Depends on the load and the original rectifier
type. Measure the B+ with an analogue meter (not a modern high-Z meter)
and compare with the schematic. If the numbers are no more than 10 or 20
volts higher, I wouldn't worry about it. If they have shot way up, I would
add some resistance in there.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."