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PostPosted: Sat May 11, 2019 2:51 pm 
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Made the plunge today and fired up my Tramp. No smoke, no fire. I had already done a preliminary check of the a/c voltages at the mains, power supply and filament power before soldering the power supply to the board and the voltages were good. Turned on the amp, set it to idle, and measured the DC voltage at the first 50uf capacitor (in my case I have 47uf) and the reading was 110vdc. I turned up the VRM slowly until I reached max setting and DC voltage was 453v. According to the builders guide, my initial reading should be over 400vdc with the VRM at idle. I then measured the AC voltage where the transformer secondary is connected to the rectifier pins. The voltage here was 652vac. The third voltage check to be done was at the second 50uf capacitor. With the VRM at idle the measured DC voltage was 453v. Turning the VRM from idle to max made little change to the DC volt reading. All of the above measurements were taken with no tubes installed and a speaker plugged in. My readings are not jiving with what the guide says I should be getting.

When I look at the layout, the readings I'm getting seem to make sense. The first 50uf capacitor (C12) is connected to the MOSFET gate, R21 (100K, 1W) to the #2 terminal of the Power Level Pot. This controls the amount of DC voltage going to the first 50uf capacitor. The second 50uf capacitor (C13) is connected directly to the DC supply at the rectifier diode junction. This would mean that the DC voltage at the second 50uf cap should always be at the rectified DC voltage I measured of 453v. This is the side of the VRM that's being supplied the full rectified voltage at pin 3 of the power level pot. As well, the first 50uf cap is connected to the OT and since this is connected to the control side of the power level pot this is how the output power is controlled.

Sure could use some clarification here. Sorry for the long explanation. :D


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PostPosted: Sat May 11, 2019 7:26 pm 
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Here's some additional information for my build. I've attached an image of the layout where I coloured all of the wired connections the same colour as the wire I used in my chassis. I've also labelled each of the components to match the schematic. As well, the speaker connection jacks that I used are not the same as those on the original layout. I used 12a shorting jacks for the internal and external speaker connections which is why I have an external ground for them. These jacks use an insulating washer so they are not grounded through the chassis. The red check marks at all of the wire connections indicate that I've measured the resistance between the two points the wire is connected through to ensure there isn't an open circuit. I've also attached an image of the layout for the dual OT mod which I did. Hopefully it will be of some help for those of you that are planning to include this mod in your build.

Attachment:
Tramp Chassis Build.jpg
Tramp Chassis Build.jpg [ 2.56 MiB | Viewed 6170 times ]

Attachment:
Dual OT Mod.jpg
Dual OT Mod.jpg [ 2.17 MiB | Viewed 6170 times ]

Attachment:
Tramp Schematic.jpg
Tramp Schematic.jpg [ 2.27 MiB | Viewed 6170 times ]

Attachment:
Tramp Layout.jpg
Tramp Layout.jpg [ 2.53 MiB | Viewed 6170 times ]


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PostPosted: Sat May 11, 2019 8:14 pm 
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T-Bone, when I checked the voltages, I put a meter probe on B+ and adjusted/set the VRM until the meter read 400VDC, then checked the points shown on the layout and also the pins listed on the voltage chart, the readings were pretty spot on (posted the readings in an attachment in state of the tramp post).

BTW, took the Tramp to a friend that can actually play and he liked it w/ the 6V6 (JJ) in but the amp had some noise. We took a break and let the tubes cool,then put in an EL34 (also JJ). The result: 6V6 sounds good, but the EL34 is SU-WEEET :lol: Ordered some new tubes from AES/Amplified Parts so I can swap out the 6V6 and track down that noise with the old 6V6.

I'll keep an eye out for your results.

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PostPosted: Sat May 11, 2019 8:27 pm 
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Just looked at the pic of your build, and am curious as to why you put the 220K carbon comp resistor on the volume control and the 220K carbon film on the board eyelet and wire that runs to pin 6 on V1? :hmmm:

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PostPosted: Sat May 11, 2019 8:45 pm 
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Hankules wrote:
Just looked at the pic of your build, and am curious as to why you put the 220K carbon comp resistor on the volume control and the 220K carbon film on the board that runs to pin 6 on V1? :hmmm:


Actually, I put a 220K carbon film resistor going to pin 1 and a 220k metal oxide resistor going to pin 6. I didn't have a carbon composition resistor and couldn't get one at my local electronics supply, all they had were carbon film. I think they would both have been fine with carbon film. Did you get the same type of voltage readings that I'm getting at C12 with the power level control at min and max? I can't see how it's possible to get 400vdc when the control is at idle. The way the circuit works it doesn't make sense.

I also installed some tubes and am not getting any kind of sound at all. The amp is dead quiet. I went over the circuit 3 times checking for open circuits or wires that were in the wrong place. Found only 1 wire that was going to wrong pin of V1. Damn! :damntech:


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PostPosted: Sat May 11, 2019 8:56 pm 
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Maybe you've grounded the output jacks. Did you use the supplied output jacks? You may have grounded the jacks in both positions (unplugged and plugged in) by wiring to the chassis star ground?

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PostPosted: Sat May 11, 2019 8:57 pm 
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sorry, don't have my amp here to use as a reference.

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PostPosted: Sat May 11, 2019 9:08 pm 
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Attachment:
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Attachment:
DSCN1478.JPG
DSCN1478.JPG [ 3.54 MiB | Viewed 6164 times ]
Here are pics of my board. Can't see the two 220k blue power resistors under first two 50uF caps.

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PostPosted: Sat May 11, 2019 11:04 pm 
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Sorry I haven't been able to help much on this.

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PostPosted: Sun May 12, 2019 12:04 am 
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I didn't use the jacks that come with the kit. The jacks I use are insulated from the chassis and get grounded separately. The jacks I used are called shorting jacks. They're normally closed by being shorted to ground when nothing is plugged into them. This is meant to help prevent hum when not being used. They require a separate ground to work properly. My power resistors are mounted under the board, not under the filter caps. I'll be checking the voltages tomorrow at the B+ locations and where noted on the schematic. Will let you know my readings then.


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