Salas DCG3 preamp (line & headphone)

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Russellc

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Power cord, IEC plug, fuse, transformers, terminal blocks all mounted and wired, disconnected power supply from pre board to test. Transformers remain cool.

One side 17.07- and 17.11+ volts each side on power supply output, other side was 17.30- and 17.34+. I s this difference something I need to address, or is this typical?

Next ( after correcting this if required) will be to reconnect pre board. Mount M1-M4 on board and heat sink. Then I can set offset and so forth , install the 8 legger and reset. Then finally wire volume pot, input/output signal wire on pre board, wire RCA grounds ( RCAs and I-select already wired) then test listen.

Thanks,

Russellc
 
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Salas

Salas

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Nothing to address, this is correct DCSTB behavior. Its a fixed output +/- PSU only relying on good tolerances of its active components. Actually your unit measures well symmetrical for fixed rails per channel. Adequate components have been applied. It also measures below the servo op-amp's max rails spec. In other words, no weirdness no danger. Well done.
 
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Russellc

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Great. Remeasuring this AM, they all read exactly 18.80, plus or minus. Letting it run a bit. This was also the first time power hit it at 120 wall voltage, no slow ramp up with variac. dont know if that did it or just hasnt warmed up yet. Letting it cook a few minutes. I will mount M1-M6 and attempt to fire it up. Leaving I-select unconnected for now, make sure all is well then clean up wiring and tap I-select to the proper place.

Russellc
 
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Russellc

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All Hooked up except wiring vol pot to board and I-select, and board to out put RCA pair. So time for fire up. For the life of me I cant find the DCG3 "guide" that goes over fire up. I thought there was a link on the first page, all I can locate now is the circuit diagram!

As I recall, turn on power, (I use a variac to slow ramp up) then adjust the pots for as low a DC measurement as possible, I understand there may be some fluctuation with out the 8 legger installed. Then power down, (I dont remember it saying to but seems logical) install the 8 legger and trim to O on offset.

Where in the wide world of sports did that guide go? Darn new computer. Almost there!

Russellc
 
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Russellc

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Couple more "pre fireup" questions. First, staring at power supply, I am wondering if it is to be grounded to chassis? Normally I do this through a CL-60, but not seeing ground from P.S. to chassis, is this correct?

Other question, in the guide under electrical testing section. The "R10 drops" mentioned, what sort of drops are we expecting to see? The instruction "The drops divided by the ohms should indicate 100-150mA". Are the drops mentioned taken by measuring across R10, and dividing that by R10's value (10 ohms?) , or do I have this all wrong?

Russellc
 
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Russellc

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Salas said:
PSU 0V through CL-60 to chassis is not a bad idea. Remove it if it brings some hum in your particular hi-fi installation. Usually it does not.
Click to expand...
So where is the best place to run the ground from PS to chassis? I'm going to have to lift the PS board to get to good place I have a feeling....will each side need its own, or are the negative sides of PS hooked together? Searching my picture list of others work...I built the power supply and mounted it some time ago, dont remember if the two side's negatives were linked or not. I see a "PE" between the 2 iN5406 and 10R resistor. Looking at board harder for PE point.

Russellc
 
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