EH-185 (Charlie Christian) build, 6SN7 PI.

Jerry garrcia

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So now the board is done. Bad ground bus. The solder didn’t attach to it. Need to find a better material. Aiming for a single ground bus.
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Jerry garrcia

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Needed to redo the component board since it became a mirror image due to the chassis style. The PT does not make sense to me if one looks at the specs and compare it with the wires The 5v is a 3A so a 5u4 will work.it’s upgraded said a note that was included. The Hammond type that I’m used to is a lot different and easier.
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mountainhick

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What's not spec about the PT?

600V CT HV: 300:0:300
6.3V CT: 3.15:0:3.15
Choice of either 5 or 6.3 volt, I assume you'll use the 5V orange wire for 5U4
 

Jerry garrcia

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What's not spec about the PT?

600V CT HV: 300:0:300
6.3V CT: 3.15:0:3.15
Choice of either 5 or 6.3 volt, I assume you'll use the 5V orange wire for 5U4
That’s something that I miss I guess. As I have 240V for the primary:
- brown-brown.
Secondary HT purple+purple, grey C.T. - filament 3.15V brown + brown (there are only three total brown wires)
- heater 5u4 pink + grey (the grey that comes from the same stack of wires as the pink?
There is a white wire?
The PT’s I’ve used before has all primary’s on one side and all secondaries on the other side. Also actually just used PT’s that can handles multiple voltages so the primary windings needs to be connected correctly. Like on the 290CAX.
Guidance please on how to connect, what the white one is and the best spot for the filament C.T. (First filter cap ground like the HT C.T. or on Power tube cathode) and why only three brown and which brown are primary and which secondary? Any logical way to tell? Never used this PT before.
 

NTC

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The primary will have a higher resistance, but to be safe you should check the turns ratios with an AC voltage.
 

mountainhick

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It looks like one of the browns is white?

I'd try to figure out first what wires are the primary. First with ohmmeter, then with low voltage on a light bulb current limiter.

Then check secondary voltages and do some math...
 

Jerry garrcia

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It looks like one of the browns is white?

I'd try to figure out first what wires are the primary. First with ohmmeter, then with low voltage on a light bulb current limiter.

Then check secondary voltages and do some math...
Only have a variac. Will try to do some reading about how to do this. Thank you. Was my suspicion to. Make more sense
 

Jerry garrcia

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Drilled the chassis and started to wire. Had to redo the board since it was mirrored due to the chassis…
Think all will fit in nice. Just two more holes when I figure out the hole sizes for the rca jacks and where to place the power jack and the PT problem and how to connect the OT. Progress.
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Jerry garrcia

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perfect! the variac is a great tool to check the PT wiring with low voltage.

After all your building do you not have a light bulb limiter?


I’ve been planning to build one but have to much stuff around. I’ll check the video and see what’s in the drawers at home😀
 

Jerry garrcia

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Needed to redo the component board since it became a mirror image due to the chassis style. The PT does not make sense to me if one looks at the specs and compare it with the wires The 5v is a 3A so a 5u4 will work.it’s upgraded said a note that was included. The Hammond type that I’m used to is a lot different and easier. View attachment 1000246 View attachment 1000247
@mountainhick @NTC
Got som alone time and took out the DMM. Continuity between brown, white and blue so should be the primaries. Checked resistance between the windings.
White-brown= 8.0 ohm
White-blue= 0.2 ohm
Brown-blue= 7.6 ohm
Then I suspect that brown is zero and white is 240V. So white “L” and brown “N” for 240 in wall? Ok deductive thinking?
 

mountainhick

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@mountainhick @NTC
Got som alone time and took out the DMM. Continuity between brown, white and blue so should be the primaries. Checked resistance between the windings.
White-brown= 8.0 ohm
White-blue= 0.2 ohm
Brown-blue= 7.6 ohm
Then I suspect that brown is zero and white is 240V. So white “L” and brown “N” for 240 in wall? Ok deductive thinking?
I agree.

I would next hook up the limiter and variac and send 12V to the Brown/White and check secondary voltages, should be 1/20 spec on the outputs.
 

Jerry garrcia

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perfect! the variac is a great tool to check the PT wiring with low voltage.

After all your building do you not have a light bulb limiter?


Just read this thing about hooking up a DMM to a variac. Wouldn’t that do the same if I measure current? Less stuff laying around and I do have two spare DMM’s.
 

mountainhick

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Just read this thing about hooking up a DMM to a variac. Wouldn’t that do the same if I measure current? Less stuff laying around and I do have two spare DMM’s.
I don't understand. DMMs are just meters, and they do measure voltage. All I am recommending to confirm correct wires for installation. You do not need to measure current to do this.
 

Jerry garrcia

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I don't understand. DMMs are just meters, and they do measure voltage. All I am recommending to confirm correct wires for installation. You do not need to measure current to do this.
I read somewhere that you could connect an DMM ammeter to the variac so that you also could measure the current. Always Fun to see the current draw. Ran away this lunch an bought me stuff to build me a lightbulb limiter.
This one looks handy.
 

Jerry garrcia

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More wiring done. Got the correct specs for the primaries of the PT. Brown 0 and blue 230V. Hopefully I’ll get that done tomorrow and also heaters, RCA and power jack drilling. Will use a power jack with a 2A fuse and also mounted one on the HT CT.
Any suggestions on where to place the power jack? The chassis will be top mounted and no space on the sides and only visible part is the side with all potentiometers. Must probably be on the bottom close to the PT (oh to place it close to the backside of the chassis between the 5u4 and 6L6?) and the RCA jacks by the reverb driver.
If anybody can detect any wrong wiring or totally crazy dressings it will be highly appreciated. Will any of the pins to the sockets need to be grounded? Thinking of using the speaker jacks ground terminal for the reverb Driver ground. The blue wires are just temporary to see if it works.
@printer2 did I remember the LNDVerb hookup correctly?
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Jerry garrcia

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Finally. A bit scared to start this bad boy up. Need to sleep on it. Placed the power socket in the wrong place. Hope that AC does not mess
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Up to much.
 

Jerry garrcia

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Really strange. Powered it up. As usual no light bulb limiter. Forgot it at work and couldn’t resist to start it.
Started first with no tubes in and slowly on the variac. PT seemed wired ok and got good AC voltages on all windings.
As I was in a teams meeting and was in a hurry to leave to the family after the meeting. Due to that I didn’t follow the RobRob start up procedure. In the retrospect it might have been a stupid idea since I didn’t have a light bulb limiter. The good thing was that I hadn’t been drinking.

So I installed all tubes and started to slowly bring it up on the variac. Since the current meeter needs > 200V to work I couldn’t measure the Current. 🤯
The rectifier worked and had DC on first node. Nothing after that. Second node no voltage. Stupid me increased the voltage up to 100V and still no voltage on second node of course. Saw a tiny amount of smoke and killed the power. PT not so hot. Reflowed the turrets between first and second node where the 10k is between but will wait to try again when the light bulb limiter is included in the circuit.

Any inputs except that I was stupid to do this without a current limiter?
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mountainhick

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Photo #2... can't really tell, but how are the filament supply wires at the lamp?

Photo #9 filament wires to tube? One looks cut/unconnected, but could it short?

There are a few scattered solder joints to tube pins that look questionable.
 




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