[Hallicrafters] OT: Fender, Joe Walsh and me.

[Roy Morgan]

At 10:52 AM 7/26/2005, Craig Roberts wrote:
>...I ordered a set of  Fender branded tubes from an online audio shop.

Craig,

That may have been your first mistake.

>...The Fenders glowed appropriately and prettily and sounded just fine. 
>(Truthfully, they sounded exactly like the old tubes) and all was well.

Sigh.. looked good for a little while!

>Well, all was well for about two hours. Then, one Fender failed.  A couple 
>of hours later, the other one went dim.

Did the first one fail in the filament, too?  If so you are lucky.  I 
remember stories of folks with antique radios (Scott, Atwater Kent, and the 
like) using 2A3's or 45's from [that huge pacific rim developing country 
that has no use for female babies].  They failed. The tubes that 
is.  Dramaticlly in some cases, taking the ancient and nearly irreplaceable 
output transformer with them.

>It seems that the Fender branded tubes are actually Electro-Harmonix 
>valves from Russia.  They're nicely made, certainly, but MAY be fragile 
>when compared with vintage American tubes.

Glad to hear your report.  There are some tubes from Russia and other 
European contries that are just superb. Example: A friend had a Dynaco 
ST-70 he'd built as a kid. I tested the thing (coupling caps were still 
fine!) and installed new Tesla E34L output tubes for him. He was running 
the thing with the bottom plate loose and it shorted the bias supply to two 
of the output tubes. They glowed very strongly red. For some time. Till he 
noticed them. I tested the tubes and found them to be exactly as I'd 
measured them when new.  With bias short removed,   they are working just 
FINE, thank you, and I was impressed.  Very impressed.

>...  Now, it's possible that I got a pair of "lemons", or it could be that 
>the new tubes simply aren't rated for the type of service the old ones were.

I think you got lemons.  Maybe the whole batch were lemons, but you won't 
know, most likely.  Electro-Harmonics is unlikely to do a recall, in my 
opinion.

There are a number or 6V6 look-alikes available in the guitar world. I 
suggest you try some other brands.  Try some 5881 types if the filament 
current is not too different and that does not worry you.

I also suggest you increase the cathode resistor in the SX-42 output 
stage.  (My downloaded schematic is completely unreadable so I don't have 
the original value at hand) so that the cathode current is at least below 
80 percent of original.  60 percent is good.

Here's an interesting exercise: operate your radio on an am station with 
your favorite speaker hooked up. Measure the actual audio output power at a 
very loud volume setting.  Then turn it up even more.. till it's VERY VERY 
loud.. and measure again. I'll bet you will discover you are using less 
than half a watt of audio power.  The pair of 6V6's is rated at some 6 to 8 
watts, is it?  Almost no one ever needs that much audio power. Period.

>... I'm a big fan of James Millen and his designs.

I wonder if you have any Millen equipment. A local friend, well known in 
the Collins circles, has recently been talked into making a web site for 
Millen equipment, with equipment-owned lists, including serial numbers. If 
you or other folks have Millen stuff and want to enter it into the 
soon-to-appear Millen Equipment Inventory, let me know. I'll post a notice 
once the thing is up and running in any case.

Roy
Who has a few pieces of Millen stuff but not many.

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan at nist.gov --