My X10 has begun

[Gee]

Surf, I found an X10 for sale that I submitted an offer. If he takes me up on it, I might have a the real thing for us to learn from.

Now we're talking!

[surfsup]

LR, that would be great to beta the two sidebyside.

Okay here's some voltage readings:

60W bulb in bulb limiter
Three readings: VVR@"10", VVR at "5" and VVR at 0 (pot turned fully CCW)

277, 250, 225 - PT secondaries
326, 241, 186 - C1 (first cap)
28.4, 117, 182 - B1 (plates)
28.2, 116, 180 - B2 (screens)
310, 231, 178 - B3 (PI)
295, 220, 170 - B4 (V2)
280, 210, 163 - B5 (V1)

2.8, 2.5, 2.3 - heater winding
1.83, 1.80, 1.86 - LED

Couple comments:
1) I don't think my standby switch is working properly because all the caps charge immediately and it doesn't seem to do anything

2) The 1k 5Ws get hot. I had the amp on about 7-10 minutes. Fuse was fine. Initially with the 60W bulb, I had the VVR at the setting where the HV was the highest (275vac) and I heard then heating and smelled them. I turned the VVR to reduce the HV and let 'em break in, then got my readings with 277VAC (above) with the amp on for a while and they seemed to acclimate (but still hot). So they seem to be holding up. (I have the 1k 6.5W vishays still in the dugout)

[angelodp]

Now thats news.... go man go.

[surfsup]

Okay some more voltages, no bulb limiter, amp plugged into the wall:

VVR@10, @5, @2.5 (at zero the HV are pretty high so I didn't keep it there)

333, 334, 334 - PT secondaries (VAC doesn't change plugged into wall)
275, 303, 352 - C1 (first cap)
270, 210, 109 - B1 (plates)
268, 207, 108 - B2 (screens)
263, 290, 337 - B3 (PI)
248, 275, 320 - B4 (V2)
236, 261, 303 - B5 (V1)
3.4, 3.4, 3.4 - heater winding
0.6, 0.6, 0.6 - LED

Questions:
-The HT secondaries are supposed to drop to 300 with tubes in, but mine are staying at 330+ (10% high), what's causing that? (all tubes are in)
-The voltages start going way up on the C1, PI, V2, V1 with the VVR toward 0 is this normal?
-The LED is not lit and here it is getting only 0.6V?
-Heaters are not getting 6.3V?

[surfsup]

Okay so everything seems to be working. The only problem I had was the NTE mosfet insulation and probably firing it up with no tubes was what burned out the 1k5Ws.

Played it, getting used to the VVR and controls. Think the pots are wired in reverse.

Slope switch: the 47k paralleled in sounds muddy, too bassy. The 200k paralleled is just a subtle change from the 100k alone.

Bright switch: my initial opinion is minimal difference between the settings. I have a 47/100pf pair to switch in, or center off.

Overall impressions: I think the lower frequencies (bass) need to be brought down some overall which might help the slope/bright switches. 1k5Ws are definitely quite warm but still blue in color so they are holding up. Guitar volume controls the gain well, seems like volume itself stays somewhat constant from 5-10 with the guitar, just distortion increases. Might be due to my MV and VVR settings. Guitar at max it is muddy. I need to clean it up some. Fast agressive amp at the higher settings though.

Edit: some hissing is present, hum is non-existent. A little oscillation sometimes but I think its due to my guitar's proximity because when I back away, it goes away (speaker and amp and guitar all within 5ft of each other)

[angelodp]

Surf, thats great, sounds like you are on to the sweep part, tweaking and adjusting.
Best A

[rawnster]

finally. let there be sound!

[Gaz]

Congrats, now the fun begins!

[surfsup]

Hmm, something's not right. Here are the power tube readings with:

272 - B1 (OT and plates)
270 - B2 screens
264 - B3
250 - B4
238 - B5

1.3mV, 2.3mV - pin 2
6.8V, 8.6V - pin 3
266, 267.5 - pin 7
270, 270 - pin 9

Problems:
1) HV: should be 300, but I'm reading 338VAC
2) VVR: turned to max, the B+ is 277VDC, as I turn it down, B+ goes up to 400VDC
3) VVR: the preamp rail voltages are changing as I turn the VVR. They are supposed to be isolated (triple checked the wiring, its good)
4) Pin 7 has lower voltage than pin 9
5) one screen is 1.3mV the other is 2.3mV, nearly double, but I assume since its mV this is not a big deal?
6) LED not coming on, only reading 0.6VAC
7) standby switch is malfunctioning, always has continuity on the side I soldered to, the other side never has continuity. I have 3 more so time to swap it.

[Colossal]

Hmm, something's not right.
3) VVR: the preamp rail voltages are changing as I turn the VVR. They are supposed to be isolated (triple checked the wiring, its good)

I presume you are VVRing the PI and power amp or just the power amp only. When you split your VVR output and preamp rail, did you isolate each run with a diode? Preamp voltages rising a bit is a known side effect of regulating just the PI and power tubes. See this schematic showing the effects of a VVR on an 18W variant: http://www.18watt.com/files/18_watt_lit ... pi_141.gif

Notice how node C2 rises when the VVR is turned down (the PI and power amp are regulated).

[surfsup]

Yea, PA scaling only, i have two uf4007 after the standby, schemo on first post w addtl pics, you can see them in this photo at end of blue lead just above the vvr board

[img2000]http://chicagocadcam.com/ChrisHahn/xen1 ... 1small.jpg[/img]

[Ian444]

I think those 2 1K resistors are upsetting the apple cart. When the VVR is turned down, the voltage drop across those 1K's will be less, forcing the preamp voltages higher.

[pamaz67]

Surf, sorry probably I'm mistaking , but what's the value of the anode resistors for the phase inverter? From your picture I see 10k, but probably is just the photo........

[surfsup]

Pamaz they measure in at 100.4K and 100.6k

Ian, I rewired the VVR to scale the whole amp. things are behaving better now but there is still a problem:

With standby switch off:
335 Unrectified
462 after diodes
*this looks right

with standby switched on
VVR@Max, VVR@Min
335, 335, Unrectified AC
274, 400, First Cap
270, 35, B1 Plates
268, 35, B2 Screens
260, 34, B3 PI
247, 33, B4 V2
238, 33, B5 V1

The problem is all the voltage values seem to drop. I am getting a high VAC before the diodes (+35vac) and a low value after rectification.

I tested all the diodes with my DMM. All test 0.44 volts approx. except one. One beeps and tests 0.0V when I DMM it, it is the one in the photo at the top left side of the VVR board. Is this diode bad?

[surfsup]

Now that the VVR is scaling the whole amp:

-definitely can see the potential where I'm at. When I find a good tone, the distortion is very smooth, WAY better than my HO.
-I still have the voltage problem where everything is low. I suspect that diode that is testing differently than the other 5 diodes. I will replace it.
-VVR at 130-150 volts on first cap sounds like a ground was crossed, then it recovers. Strange, but may be due to the diode/voltages
-Slope switch three positions really change the tone: more bass, middle of the road, slightly higher
-Bright switch is still minimal effect with 50 and 100pF caps.
-Still bassy overall I think - or just too much gain. Higher voltages might help. Might go with a smaller R for the RC between the PI and MV; also might swap out some Rs at the grid leak into stage three once the V problem is fixed

[img1000]http://chicagocadcam.com/ChrisHahn/xen10/INPUT.jpg[/img]