To: <amps@contesting.com>
>Date: Sun, 11 Apr 1999 21:57:13
>To: Gudguyham@aol.com
>From: Edward Pagaduan <ezed@mail.aloha.net>
>Subject: Re: AL-1500
>
With the blown primary fuses, Found out it was those filter (Philips)
capacitors arcing and shorting out. One I had, didn't have a step start
circuit. How does the circuit in yours look like? Is a resistor switched
in the plate & filament primaries at start up? I'm just using a NEMA 6-20R
for the circuit feed to my amp protected by a Challenger 2 gang breaker.
Used to be GFCI in the circuit but pulled it out due to RFI on 160. My
AL-1500 had an extra hole but patched over. Why did you choose the al-1200
to modify, does it have more room?
4300 volts is a bit steep for an 8877. Its rated at 3600 volts by Eimac. I
saw in the Radio Handbook by Bill Orr a homebrew amp with 4300 volts running
on the plate of an 8877.
I'm still figuring out why my amp didn't have a parasitic choke with that
expensive tube. Does your AL-1500 have a parasitic choke on the 8877 plate
lead? Also figuring out how come it did not look like there was not enough
of those 450 volt rated Philips capacitors in series for filtering. Had 8
in series. Figured it would take 11 (5540 volts total max.). Maybe
Ameritron did some improvements in their newer model besides giving it a
stainless chassis. Bought mine in 1988. Also looking at the Henry and
Alpha line of amps. Henry has resonant power supplies which, in my
experience in other types of equipment that use similar power supplies, not
that reliable. Transformers and chokes tend to go early when they're
running near saturation. Alpha is a bit too pricey. That autotune
microprocessor gear cost a lot but still a little too touchy.
Good luck in your amp conversions.
Ed
ezed@aloha.net
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