Well, I spent the whole day going through the chassis again end to end. Here is what I did. I started with the speaker. The Output transformer ohmed out good as did the field coil. I checked the wiring to it, also good. I ohmed the part #57 came out at 263 ohms. Almost perfect. I checked all coils in the unit and they were all good and really close in the numbers. I traced all wiring and marked it on a new schematic. I checked my electrolytics and how I connected them on the terminal strip. All correct. I checked all resistors. I did find a mistake on part #46. I had 4.7k resistors in my drawer for 490K by mistake so I had installed a 4.7k. I reversed this to a 490k. I rechecked all the tubes. The 42 tube still showed low a little under 60, maybe 59. I did order a new one. I fixed the 750k resistor that was low and now it is ohming at 754k. I checked how I hooked up the transformer and ohmed it too just to make sure I didn't cross a wire. I said all this because when I powered back up I am having the same problem. It is acting like there is no load. I know my problem is on the front end at the 6a7 or before. I can touch the other grids and get noise in the speaker. If anybody has any more ideas it would help. By the way by changing out the resistors the voltage on pin 1 and 4 on the 80 tube went down to about 338vdc.
Let me ask this: when warmed up, if you touch (careful, sitting or standing on an isolated platform) grid cap of the 75 or pin 4 of 42 tube, do you hear the AC hum?
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 01-23-2017, 05:00 PM by morzh.)
I'm just getting a hum from the speaker and I haven't hooked up a signal generator yet. In answer to your second question, I had to order a 42 tube which I did.
I have been away for a little and just getting back to this 610. I found out that the 6A7 did have problems and replaced it. It works from the 6a7 forward but I still have something wrong on the front end of this thing. The field coil and voice coil are good as well as the opt. It is like it doesn't have a load. The 80 tube is still showing 385 vdc on pins 1 and 4 and 785 vac across pins 2 and 3. By the way part 57 is perfect. I disconnected and re checked the transformer and the only thing that ohms a little high is the primary side. It was 7.2. Everything else is really close especially the secondary going to the 80 tube. I checked my connections in all areas leading up to my 6a7 tube just to make sure I didn't wire something wrong. I did have a thought. This may be a rookie question but when I was cleaning tar out of block number 32, I didn't realize until too late they were mica caps. If I bought the wrong replacements or wired these wrong would this cause the above problem. It is showing really high negative voltage at this block.
Yes, got a new 42 and 6a7 and no change with the result. I don't know what else to do. This thing should work. I didn't think so on the mica caps but I wasn't sure. Thx
Can I put a load across it using a ceramic resistor to simulate the field coil and see if my voltages come in line. I'm thinking this would further test if the field coil is working right. I did a 9v battery test on the field coil and that worked. If I did use a resistor to test, would I put it between the positive end of the two 8mf e-caps? Probably another rookie question? lol
Just to be sure, you're getting 1100 ohms when you test your field coil by putting your ohmmeter across the positive terminals of the two 8uf caps?
Keith
Also, be sure the band switch is fully counter clockwise. Without a knob and turning the shaft by hand it's easy to think you're turned fully counter clockwise when in reality you're on another band. This just happened to me on my 610 and had me confused for several hours.
keith
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