[Amps] Alpha 86

[Dick Green WC1M]

FWIW, a member of our contest club had problems with massive IMD
interference to other radios caused by bad PIN diodes in a used Alpha 86 he
bought. Being a thrifty fellow, and not needing QSK for multi-multi
contesting, he simply bypassed the PIN diodes with a standard relay-based
T/R switching system (not even a vacuum relay.) Aside from the PIN diode
problem, my understanding is that the RF portion of the amp is excellent and
a real workhorse.

73, Dick WC1M

> -----Original Message-----
> From: SamuelR717 at aol.com [mailto:SamuelR717 at aol.com] 
> Sent: Sunday, June 05, 2005 11:59 PM
> To: amps at contesting.com; n4dek at triad.rr.com
> Subject: [Amps] Alpha 86
> 
> 
> N4DEK wrote
>  
>  I have just purchased an Alpha 86 amplifier that is supposed 
> to be in  like 
> new condition inside and out and working perfect with full 
> output. This is  my 
> first Alpha amp and I am interested in any pros/cons that I 
> need to be aware  
> of with this model. I'm curious about all the talk about the 
> PIN diodes being 
>  weak in this one. What if anything do I need to do to 
> protect these from 
> being a  problem? Do I need to keep some spare fuses on hand 
> for this? Any and 
> all help  welcome.
> 
> Thanks,Don
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  
> Base on my experience, get a large supply of the small 
> receive fuses!   I had 
> an 86 for several months; it was a fine amp, EXCEPT for the 
> pin diodes  
> causing the receive fuse to blow every 4 or 5 times I used 
> the amp (into a quad  
> with flat SWR on all bands).  When the fuse blows, the amp 
> still functions,  but 
> you can't hear anything unless you manually switch into 
> "Standby"  mode.  Not 
> fun trying to break a pile-up that way!  I must admit that  I 
> hoped the guy 
> who sold it to me (without mentioning this problem) would  
> develop some kind of 
> very unpleasant skin condition...
>  
> I had LENGTHY conversations with Alpha Tech Support.  I 
> replaced  the pin 
> diodes, at their suggestion, which had no effect (which they 
> warned me  might 
> happen).  Their final word was that not much could be 
> done--some 86s  had this 
> problem, some didn't, and they really didn't know why or how 
> to fix  it, short 
> of pulling the pin diode system and replacing them with 
> vacuum  relays.  They 
> also warned me NOT to use a higher rated receive fuse, at  
> risk of blowing the 
> HV PS.
>  
> I finally sold it (at a loss) to a W6 who is a broadcast 
> engineer, and who  
> rebuilt it with hi speed relays and re-sold it.  
>  
> I eventually brought a used 87A. I  had some initial probs, 
> but worked  thru 
> them with help from Tech Support, and it has served me well 
> for the past 2  
> years.  I still like Alpha products, but they seems to have 
> gone astray on  the 
> 86.
>  
> Good luck, and 73
>  
> Sam
> AA3VD
> 
>