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Re: [Amps] Dentron amplifier problems

To: "Tim Kass" <k8wbl@yahoo.com>, <amps@contesting.com>
Subject: Re: [Amps] Dentron amplifier problems
From: "Jim W7RY" <w7ry@inbox.com>
Reply-to: Jim W7RY <w7ry@inbox.com>
Date: Sat, 19 Mar 2011 11:23:39 -0700
List-post: <amps@contesting.com">mailto:amps@contesting.com>
The Dentron 10-160L is supposed to have 572Bs in it.  How much high voltage?

73
Jim W7RY


--------------------------------------------------
From: "Tim Kass" <k8wbl@yahoo.com>
Sent: Friday, March 18, 2011 1:25 PM
To: <amps@contesting.com>
Subject: [Amps] Dentron amplifier problems

> Hello Group... I took over this project just recently when I purchased 
> this amp from Ron, NR8O ..  here is his original post...amp has apparently 
> been sitting since that time..
>
>
> [AMPS] My dentron 160-10L
>
>
>
>
> from [Ron Rollinson]
> [Permanent Link][Original]
>
>
>
>
> To:
> <amps@contesting.com>
>
> Subject:
> [AMPS] My dentron 160-10L
>
> From:
> ronr@nowonder.com (Ron Rollinson)
>
> Date:
> Wed, 03 Mar 1999 01:04:50 -0500
>
>
>
>
> Hi folks, I've only been subscribed to the list for a couple of days but I
> can tell there is a lot of knowledge floating around here regarding amps.
> I don't know if it's related in any way to me subscribing to the list but
> the other day, there I was on 20 meters cw when my Dentron 160-10L
> (4-811a's) made a loud bang and popped the breaker in the back of the amp.
> When I opened it up I noticed one of the tubes appeared discolored and in
> the process of removing it the parasitic resistor in the plate line easily
> broke in half.  One thing I noticed is that this particular resistor must
> have been replaced previously but a carbon resistor wasn't used, instead 
> it
> looks like one of those metal film tv type resistors...  Anyway, the 
> damage
> is done, one tube is shot, and there appears to be a problem with the 
> plate
> supply, I'm only getting about 1000 volts and a weird buzzing noise.  I'm
> sure I can troubleshoot the plate supply and get it running again but 
> while
> I've got the thing apart I'd really like to do some mods to it (Step start
> for one).  Since I've seen very little disussed here about 811A amps I 
> have
> several questions.  Should I consider updating the parasitic suppression 
> in
> the plate line (could this be what fried my amp to begin with)?  Are there
> any other things I should consider doing such as grid current protection,
> high speed t/r switching, etc?  I actually kind of like this amp but I've
> been unable to find anything in back issues of QST or on the net as far as
> mods or updates.  Any advice or info on this amplifier would certainly be
> very much appreciated!
>
> 73, Ron NR8O
>
> I have since replaced the bad 811A, which likely shorted out...replaced 
> the RF choke with a larger AL-572 choke and also a new harmonic supression 
> board on top of the 811A's.. close fit..replaced the glitch resistor with 
> a 10 ohm 10 watt variety... replaced the 1 amp diodes with 3 amp 1000 PIV 
> jobies but still only getting 1000 VDC out.. brought up the amp slowly as 
> well with a variac.  There have been some mods to this amp as well. 
> Someone replaced the meter switch with a 3 position switch and, according 
> to Ron, was a by-pass switch.  I removed the wire on this as to try to 
> make this original to the original schematic and go from there.  Now... at 
> this point I think I have to consider checking and/ replacing the 
> electrolytic caps... could some of them being open cause this low voltage 
> situation or could it possibly be a problem with the primary transformer 
> (heaven forbid) and costly..   Thanks for any input into this project.
>
> 73, Tim K8WBL
>
>
>
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