Twist Turner

Need Pultec Eqp-1a Help - no make up gain?
« on: November 28, 2007, 08:39:19 PM »
Hi Guys,

I'm finally getting around to building something from scratch again. I have my Pultec EQP-1a nearly completed. Used the original tube design as diagramed by Cayocosta. I used a HS66 input, and Sowter interstage, output and inductor.

I just got it done and fired it up(no smoke!). At first no signal, but after about 4 hrs I tracked down 1 misplaced wire. I've been over everything else with a fine tooth comb and I don't think I'm getting any make up gain. I'm a good 15db below what I put in there whether in bypass or not.  I am getting signal and the eq section is working(and sounds great too)

Is there somewhere specifically I should be looking?  I know the diagram is a little vague when it comes to the transformers, but I think with the help of the schematic I have that worked out. The tubes all test good and no shorts.  I've got a feeling my problem is possibly in the interstage or output hook up. Any ideas where to start. I can only give this one more day and then I'll turn it over to my tech, but I'd rather solve it myself if at all possible.

I also just noticed I could hook up the output secondarys at 10:1 or 5:1 I have them as 10:1 right now, is this ok.

Also I'm running the input in at 600 ohms should I possibly switch that to 250 or 150ohms input???

Twist Turner

Need Pultec Eqp-1a Help - no make up gain?
« Reply #1 on: November 29, 2007, 01:13:25 PM »
I've been looking this over some more and have a couple questions if anybody can answer.

1) The wire shown going from one of the 33uf caps going to the output trans. From the schematic this looks to be going to the center tap of the primary, would that be correct? For what it's worth I've tried connecting and not and it works both ways but my problem still exists.

2)I really think my problem is in the transformer wiring.  On the HS66 for 600 ohms I need to connect 3-4, ct. But I see no pin marked center tap and I can't find a diagram of the windings(I know I've seen these but have searched the net for 2 hrs with no luck)  right now I just have 3-4 jumpered and 1-6 connected. anybody know which is center tap on the hs66???


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