Problem with Cinemag and AA 2006 phono.

[SY]

I chekced between coils, the resistance were in terms of Mohms, then slowly decreasing to kohms... is this normal?

If the transformer is isolated from the circuit, then no, that's not normal.

I don't remember, do you have a scope? It might be interesting to see if the transformer could be causing an oscillation. You are using the MM input?

[pengboon]

Hi SY,

Let me check again, which wires should I measure across?

I don't have a scope, using MM input. Is it possible the transformers are interacting with the input capacitances? This phono has absolutely no problems with my denon 1:10.

[SY]

Disconnect the transformer and measure between any primary and any secondary lead. Should be open circuit, as should any of those wires to case or shield.

Looking more and more like you've got some defective transformers.

[pengboon]

I measured, they are in the Mohm range, at least 1Mohm, then slowly the DMM reading goes up (my mistake previously in saying it goes down)...

[SY]

A scope would confirm it, but I think the transformers were wired wrong internally; they came out of the same batch, presumably? I've seen this happen when multiple sections are connected internally out of proper phase. This would be a good time to contact Cinemag.

[pengboon]

I have, thanks SY! they were bought as a pair, so I would think they would be from the same batch.

[kevinkr]

Is there any possibility that the input of the phono stage is being overloaded by the voltage gain provided by this transformer which for the 37 ohm input would be about 37:1 and for the 150 ohm input about 18:1? This is substantially more gain than the 10:1 transformer it is being compared against.. Just a thought..

Cinemag makes very good stuff and has excellent QC on their products, while it isn't impossible I would be very surprised if something was wrong with those transformers.

[SY]

You'd think so, wouldn't you? But I have some input trannies from a first-line manufacturer (much more expensive than Cinemag) which had exactly that problem- the secondary coils were connected out of phase internally. The manufacturer acknowledged the issue somewhat sheepishly and would have replaced them without hesitation.

[pengboon]

Originally posted by kevinkr
Is there any possibility that the input of the phono stage is being overloaded by the voltage gain provided by this transformer which for the 37 ohm input would be about 37:1 and for the 150 ohm input about 18:1? This is substantially more gain than the 10:1 transformer it is being compared against.. Just a thought..

Cinemag makes very good stuff and has excellent QC on their products, while it isn't impossible I would be very surprised if something was wrong with those transformers.

My cart is spec-ed at 0.3mV, and I load it with 18.75k on the secondary, so on the primary it will be about 14R, same as the cart. This should result in about 5+mV into the phono. Will this overload the phono?

[SY]

If 5mV overloads the phono stage, that's a pretty weak phono stage.