[Top] [All Lists]

[AMPS] Caveat on Dentron Filaments + MLA-2500B Notes

To: <>
Subject: [AMPS] Caveat on Dentron Filaments + MLA-2500B Notes
From: (measures)
Date: Sat, 29 Jul 2000 17:00:48 -0700
>As you can probably guess by my posts, I am refurbishing
>a Dentron MLA-2500B amp.
>This model, and most of the Dentron power transformers
>were wound for 234 volt mains. (Alpha's were also, for that matter) I 
>measured 6.75 volts on the tube pins of
>those expensive 8875's in the 2500B. I wound six turns
>of #22 teflon covered wire on a one inch form and placed it in series with 
>the side of the filament winding that goes to ground. This reduced the 
>voltage at the tube pins to a comfortable 6.18 volts. This will also serve 
>as a "bump" for any in-rush current that may or may not be there. (I don't 
>have anything to measure inrush with)
>I am very interested to chat with anyone that has played with MLA-2500B's. 
>The padder door knob caps vary from model to model, and even within a 
>model. Since the load cap is only 500 pf, this presents a very narrow 
>for matching various loads on 160 meters, as most of the
>capacitance is fixed in the padders. Also, various values
>of padders on the tune cap are used from model to model 
>depending on what value it is...140 pf on the older models and 170 pf on 
>the "B" model.
>All in all, the MLA-2500B is a sweet, 

?  The MLA commits one of the worst layout errors known --too much 
distance between the anodes and the Tune-C.  According to Willis Foote,  
Dennis Had sent Eimac the engineering prototype of the MLA-2500 for 
evaluation, Eimac's engineers were somewhat shocked by the lack of good 
engineering.  They wrote an engineering investigation report and returned 
it and the unit to Dennis Had.  .  Incredibly, Dennis did not incorporate 
any of the recommended changes.  MLA-2500s were commonly frequented by 
VHF and UHF oscillations.  There were many returns.  When Dentron filed 
for bankruptsy, Eimac had not been paid one cent for hundreds of 
kilobucks worth of tubes.  

> .  compact, legal-limit
>amp with no bad habits and very smooth tune-up. 

?  [chortle].  

>Too bad
>that the 8875's are becoming extinct!
?  Someone should make a horiz fan cooled version of the 3cx800z7.

later, Phil

-  Rich..., 805.386.3734,  

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>