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Re: [TenTec] Titan 425 plate current meter needed - Floyd & Allen

To: "er_araujo@yahoo.com" <er_araujo@yahoo.com>, "tentec@contesting.com" <tentec@contesting.com>
Subject: Re: [TenTec] Titan 425 plate current meter needed - Floyd & Allen
From: A R <raf_3@msn.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 9 Oct 2016 03:31:09 +0000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Glad you're able to get the 425 healed. It's my favorite TT amp. Was the meter 
cost from Jewell-Modutec comparable with the cost from Galco.com ($34)? I'll 
certainly be interested in how you do.

BTW, my Centurion with the blown meters (really low and inconsistent readings) 
also had suffered a failed Q1 bias transistor on the 81537 FILAMENT-AC Board. 
The ham that I got the meters from told me that the original meters in his 
Centurion failed as a consequence of (or, at least coincidentally with) the 
failure of the Q1 bias transistor in his amp (must have created one helluva 
spike). He is a very accomplished, seasoned EE, and suggested installing 
"snubbing" Zeners across the meter leads. Per his suggestion, I have installed 
1N748A 3.9v zeners across the meter leads (cathode on + lead) in both my 
Centurions and Titans, with no adverse effects on normal meter function. 
Whether or not limiting the "spike" current thru the meters to ~160% of rated 
full-scale current will prevent damaging the Modutec meters is yet to be 
confirmed. Fortunately, I haven't lost another Q1 bias transistor. But, the 
zeners are cheap, easy to install, don't affect normal meter function...so may 
be worthwhile protection for the Modutec meters.

Best 73,

----- Original Message -----
From: Eduardo Araujo via TenTec<mailto:tentec@contesting.com>
To: tentec@contesting.com<mailto:tentec@contesting.com>
Cc: Eduardo Araujo<mailto:er_araujo@yahoo.com>
Sent: Saturday, October 08, 2016 6:48 PM
Subject: Re: [TenTec] Titan 425 plate current meter needed - Floyd & Allen

Hello Floyd, Allen and rest of the group,
First of all many thanks for the valuable information.Let me add my two cents 
commenting on what I have found and done so far.
". I suspect the Titan meters are the same or from the same source. Google 
"Modutec Jewell 2MAS" and takea lookat those meters. "
Titan 425 definetely use Modutec 2MAS-DMA-001 with a custom scale. The factory 
does not have original scale but they could make a customized one for 170 US 
above meter cost.
I though about two options, one is described by Allen and it is to replace the 
new electrical/mechanical elements into the old body, that would allow me to 
use the original scale. As I already did an autopsy of the dead meter, Allen 
comments confirmed me that the exchange could be done relative easily, Many 
thanks Allen too.

The second alternative was to print a meter scale with a SW same as you suggest 
Floyd but the factory print the scale directly on the meter plastic body 
surface, so I would have to remove the printing before use a printed paper 
scale on it, otherwise and as the light is from behind, both scales would be 
As I was not able to get from the factory a catalog with scales they have 
readily available at no extra cost in order to find which one could fit more or 
less similar to the original, and also to avoid both scale superimposed, I 
requested the factory to do not print the scale on the meter, so they will 
(hopefully) provide me with a Modutec 2MAS-DMA-001 with blank scale (at no 
extra cost) which would be useful for both alternatives.
"On my Centurion, I found that the plate current meter full scale current 
should have been 1 ma. but my meter (and those of some other people) actually 
measured 1.33 ma for full scale."
I don't know the original because it was already dead when I recently both the 
amplifier but I have another 425 of same generation and the meter measures 
1.022 mA FS with 2.60vdc across its terminals which means an internal 
resistance of 2540 ohms.
I swear I saw 2MAS-DMA-001 spec as having 2300 ohms which would need 2.3vdc to 
Considering what you and Allen wrote, that makes me wonder because on the 425 
they measure the voltage drop across a 1.5 ohms resistor and the meter scale is 
1.5A FS, so, 1.5 x 1.5, would provide 2.25 vdc. That would be 86.5% FS of my 
other meter or aprox 1.3A so if did the math right, something doesn't match.... 
I will check that
"A few weeks back I emailed Tentec with a question about the Centurion and it 
took just over two weeks to get a response. They told me that all the amplifier 
stuff was still in a warehouse somewhere and they were not in a position to 
supply parts or information at that time"
Many thanks for the great update, at least you got feedback, They didn´t answer 
me (yet).
So as a resume, a Modutec 2MAS-DMA-001 is being produced for me with blank 
scale and would be ready for first or second week of November....
When I get the meter and check it electrically I could update here if you guys 
think it could be useful.Eddie, LU2DKT
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