Gillespie Mod for Eico HF-60

kohngallery

kohngallery

New Member
Speaking of The Gillespie mod for the Eico HF-60, I am attempting to execute the instructions...but I am pretty unskilled at reading schematics and trying to teach myself. For example, the old driver plate resistors R11 and R12 were difficult for me to follow from the schematic. But I went to the original Eico instructions and they are noted as resistors next to the speaker outputs. Is that correct? Similarly, coupling caps C9 and C10 are shown as C10 mounted on the chassis near the tubes, and the C9 again near the speaker terminals. Any suggestions will be greatly appreciated.
 
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No R11 and R12 are mounted on the second 6SN7. C9 and C10 are connected to them respectively.

There is nothing near the speaker connector, just R22 R23 C13 C12 part of the feedback network (attached pic).

I suggest you take clean picture of your amp, then follow the schematic, and mark your picture with the label according to the schematic.
It's a tedious process but this makes finding your way from the schematic to the real world very easy.
 

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The mod instructions suggest a filter choke of 30H 50mA and at least 1300ohm. The choke I purchased is the Hammond 194E, 30H, 100mA and 517 ohm. In order to use this choke should I add the 1.3k, 1/2 watt resistor?
 
You want the total DC resistance at that location to be 1.3k. If your choke has DC resistance of 517 ohms, then you want to add an additional resistor in series with the choke of size 783 ohms. But that's close enough to an E24 value of 750 ohms. I assume you are not adding the big 3H 300 mA choke in between C1A and C1B.

By the way, adding that 750 ohm series resistance or not, is only going to change voltage at the node labeled "475V" by about 6 or 8 volts, so adding it or leaving it out will make little difference overall. What you really want is 475V and 180V at those points on the power supply portion of the schematic as labeled, and in your case you may need to add a larger or smaller resistor to achieve that.
 
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Thank you for the clarification. I will add the 750ohm resistor to the 517ohm choke and see what the reading is. Much appreciated!
 
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