yet another Merit mystery transformer

[N3DRB The Derb]

well sort of. it says driver on it and A-4047 30 W var ratio. None of the usual on line sources have it listed. Anyone have a merit catalog with this gem in it?

I gather its a 30 watt audio driver transformer, but the type of driver (class B?,) and ratios would be nice to know.

[KB3DKS]

Hi Derb !
1950/51 shortform info is Line to Grid Class B Grids 30 Watt Capacity
1:.75, 1:.85, 1:1, 1:1.25, 1:1.45, 1:1.75, 1:2, 1:2.25, 1:2.50, 1:2.75, 1:3
Sorry, no connection diag.
Good Luck !
Bill
KB3DKS in 1 Land

[N3DRB The Derb]

thanks Bill! I was hoping thats what it was. I'll run some low level ac through it and figure out the pin outs. I'm not going to be using it right away - nice bit of iron to have stashed away. I'd bet money the other mystery unit I have is the exact same unit but 20 years earlier manufacture - same case, same terminals, and it came out of a 1930's speech amp/ audio amp.

What I'm going to need is a 20 watt P-P output transformer that matches low impedance tubes and has a 500 ohm line output. I picked up a UTC CG-59 AX which is going on the big modulator deck- 500 ohm line to class b grids. I might put the speech amp in the rack, in which case the merit might get used. I like knowing I can go both ways.

tanks. 

[w1vtp]

<snip>... I picked up a UTC CG-59 AX which is going on the big modulator deck- 500 ohm line to class b grids. I might put the speech amp in the rack, in which case the merit might get used. I like knowing I can go both ways.

tanks. 

Same plan here.  Got my CG-59AX from Tom 2ILA.  I'm trying to figure out how to match the 500 ohm input Z to my Bogen M-60 amp.  I'll look at my xfmr catalogue collection to see if I have anything on your Merit..

Al

[k4kyv]

Hi Derb !
1950/51 shortform info is Line to Grid Class B Grids 30 Watt Capacity
1:.75, 1:.85, 1:1, 1:1.25, 1:1.45, 1:1.75, 1:2, 1:2.25, 1:2.50, 1:2.75, 1:3
Sorry, no connection diag.

Those ratios look more like plate(s) to grids.  If "line" means 500/600Ω, 1:.75 makes for an awfully low grid impedance.  The 1:2 t o 1:3 step up ratios look more credible as line-to-grid, but those are also common plate-grid driver ratios for triodes  running in class AB1 or AB2 where a large grid voltage swing is needed.

If it is indeed line to grid, it should be interchangeable with the CG-59AX.

I used to have one of those here, but I probably let someone else have it.  I never liked the idea of using two transformers between driver plates and class-B grids, thus doubling the degradation of driver plate regulation due to resistive losses and leakage reactance.  My homebrew transmitters all use push-pull plates to push-pull grids class B driver transformers.

[N3DRB The Derb]

well I could use one of my S-9's i guess. I have a extra I nabbed offa ebay brand new. I used a UTC PA 53 AX in the first HB rig - dont remember what the output transformer was on the speech deck, just that I used a pair of 2A3's in it with a dual triode ( I think a 6SN7)driving the 2A3's. check out the 6SN7 transformer going to the 2A3's - how oversized was that?!  my one concession to modern electronics was that I just happened to have some 62 volt zener diodes and clamped the 2A3 bias with them. It was making more than 10 watts for sure. It just never seemed to run out of gas no matter how hard I swung the munky. I musta had all the ratios perfect.

That modulator had the Thordarson CHT 300 watt job in it - the M77. That modulator could pin a 500ma meter, it had a lot of extra in reserve, and it sounded damn good.


I forgot to mention - that braided twisted pair in the middle is the 500 ohm output from the speech deck going into the mod deck......so I ran all of maybe a foot of 500Ω line! Didn't know any better. 

not seen is the 22.5 volt bias battery I used to bias the 805's with....gonna use a 45 volt with the 810's. I like battery bias on modulator tubes.

[KB3DKS]

Same plan here.  Got my CG-59AX from Tom 2ILA.  I'm trying to figure out how to match the 500 ohm input Z to my Bogen M-60 amp.  I'll look at my xfmr catalogue collection to see if I have anything on your Merit..

Al

Al,
The CG-59AX also can be wired for 50 ohms according to the UTC data.
The Bogen has a 70 volt line output which is usually 50 ohms so you are good to go.


Bill KB3DKS in 1 Land