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Author Topic: Troubleshooting OTS 50w  (Read 7298 times)
parrosa
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« on: October 06, 2013, 02:19:01 PM »

Hi all,

 After 20 and some hours, i finished the OTS... and the result is just static, to my desapointment  Huh?   So i did something wrong along the way Sad

I had a lot of doubts during the build. If any of you can help or just tip, please type Smiley


I have doubts regarding the Transformers.... Mcinku was kind to send me a picture with the correct wiring for this PT. I've managed to copy it, but i don't know if it's still well connected. With the PT comes a colour code for the wires. I wrote it on "PT wire codes.jpg" (very small numbers, sorry).

The two wires from the choke are not differentiate?

The Primary of the OT has 3 wires, two wires for lug nº3 of each 6l6; The third goes to the 200uf Cap, with a choke wire? It's there on the schematic, but i'm not sure if im reading well...

Another thing about the schematic is the power amp in and preamp out jacks. The perspective of the schematic tells me wires N and T are on the lugs closer to chassis. But on Ceriatone OTS pics, you see the other way around... So i followed the pics.



 


* Wiring old.jpg (987.75 KB, 2592x1944 - viewed 170 times.)

* Wiring new.jpg (974.04 KB, 2592x1944 - viewed 146 times.)

* PT wire codes.jpg (1244.54 KB, 2592x1944 - viewed 144 times.)
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parrosa
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« Reply #1 on: October 06, 2013, 02:27:12 PM »

Another thing about the PT; it has 3 red wires. 2 with 340v, 1 with 3,15v. I'm just guessing wich is wich...

I have double checked all the wiring, nothing i could spot wrong.


* top view.jpg (1085.83 KB, 2592x1944 - viewed 157 times.)

* panorama.jpg (1338.33 KB, 2832x624 - viewed 143 times.)

* side view1.jpg (1120.33 KB, 1944x2592 - viewed 149 times.)
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parrosa
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« Reply #2 on: October 06, 2013, 02:39:43 PM »

some more pics


* back left.jpg (955.28 KB, 2592x1944 - viewed 150 times.)

* back right.jpg (980.77 KB, 2592x1944 - viewed 154 times.)

* pots1.jpg (1405.75 KB, 2592x1944 - viewed 129 times.)
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wyatt
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« Reply #3 on: October 06, 2013, 07:06:03 PM »

First step is to pull all the tubes and measure all your voltages with a DMM.

Post the voltage measure at every pin on each tube socket...

If you built a lightbulb limiter to test for shorts at first start-up...and I advise you should have one...you should use it and check for any symptoms of a short-circuit.

Once we've determined if the voltages are correct throughout the amp, then we start tracing for breaks in the circuit. This is best done with a signal generator and a O'scope, but it's far cheaper to make a probe that can be run into another amp.

Building an amp is far, far easier than troubleshooting one.

I don't understand your comment on the effects loop...the layout looks exactly as the pictures show it wired (including your own pictures) Still, NEVER defer to the pictures, the were often taken of amps built with older layouts or different parts. On many of the Ceriatone models, the chassis in the pictures looks nothing like the current chassis/layout.

Last, what Ceriatone supplies is a layout, it is NOT a schematic. There is a big difference between the two, the layout shows the mechanical connections between the parts, but often leaves assumed details, that are the same across all tube amps, out (like filament wiring). But more importantly, if you use different parts, the connections can change as well.

« Last Edit: October 06, 2013, 07:08:50 PM by wyatt » Logged
parrosa
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« Reply #4 on: October 07, 2013, 11:33:01 AM »

Thanks Wyatt, gonna dig for those measures right now....

Sorry about the technical names, i lost most of my electronics knowledge. I've learned 4 years in electronics, but stopped around 1999....


BTW, how does these input jacks look to you?

Thanx


* input jack detail.jpg (263.28 KB, 1099x901 - viewed 145 times.)
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parrosa
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« Reply #5 on: October 07, 2013, 01:39:03 PM »

Already turned it on for a minute, the only sound i get is static....

I have it working with tubes and on standby, it measures the following:

V1

1 - 380mv
2 - 400mv
3 - 60mv
4 - 0
5 - 0
6 - 390mv
7 - 610mv
8 - 10mv
9 - 0

V2

1 - 490mv
2 - 550mv
3 - 30mv
4 - 0
5 - 0
6 - 430mv
7 - 630
8 - 1
9 - 0

V3

1 - 290mv
6 - 290mv
all other pins read 0


should i take the tubes and measure every pin?
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wyatt
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« Reply #6 on: October 07, 2013, 02:21:48 PM »

First, pull all the tubes pout...you don't need them to check voltages and if you have the power tubes in and no speaker load hooked up, you'll fry the output transformer.

When you measure, connect the black probe to ground (alligator clip works best), and place the red probe on each pin. Keep the free hand in the pocket (for safety).

But those measurements aren't right...not at all.

First off...you don't have any filament voltage...that's pins 4/5 (connected) and 9 on the 12AX7's. The tube should be seeing 3.15VDC on pins 4/5 and 3.15VDC on pin 9. Are you measuring 3.15V with the PT hooks up to the terminal strip ebfore going to the tubes and pilot lamp?

According to this...
www.ceriatone.com/voltage/VoltageChart.xls

You should see...
~200 volts (NOT millivolts) on your plates of V1 and V2 (Pins 1 & 6) and ~300V on the plates of V3.

So, we have multiple issues going on, many may be related to PT wiring. Strat measuring the voltages were each PT lead makes it's first connection and make sure you have the right wires connected. If you don't, you may have damaged other parts.

This is going to get difficult to do online, eventually, you have to buck it up and see one of these...
http://ceriatone.com/tlbrBorderSub/tech_service.htm
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parrosa
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« Reply #7 on: October 07, 2013, 04:12:03 PM »

Thanks wyatt, i'll try your advice before taking it to a tech...
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wyatt
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« Reply #8 on: October 07, 2013, 07:02:19 PM »

Thanks wyatt, i'll try your advice before taking it to a tech...

Well, there is a lot of stuff we can work through. One winding at a time.

The first is the 3.15-3.15 filament winding. Make sure you get 3.15V (to ground) on both halves of the winding connected at the terminal strip. Does the pilot light come on? Make sure you are getting 3.15V (to ground) at the pilot light.

If the voltage is correct at the terminal strip...follow the next wires to V5 and measure at Pins 2 and 7. If it's correct here go to V4...if correct there...well we know V3 isn't seeing the filament voltage, so there has to be a short or an open circuit somewhere between the PT and V3. Let's track it down.

On a related note, do you know if one of those green wires is a center-tap for the 3.15-3.15 winding?

Once we have the filaments working, we'll move to the high voltage wiring.
« Last Edit: October 07, 2013, 07:07:59 PM by wyatt » Logged
parrosa
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« Reply #9 on: October 07, 2013, 07:29:07 PM »

this is what i've got without tubes:

PT secondary taps:
55VAC
374VAC x2
3,4VAC x2
15VAC x2
0V x2

OT Primary taps:
507VDC x3

I've re-checked the connections from these taps on my build, and they seem to be according to the layout...

Measured some connections :  3,4V at pilot light wires and heaters, 6L6's pin3 with 507VDC; 30V to voltage regulator and 25,6V out...
Maybe i just misread the DMM  at the first time  Embarrassed  im going to measure again with the tubes tomorrow and compare them with the chart.

Just receveid your reply, ill answer after....
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parrosa
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« Reply #10 on: October 07, 2013, 07:48:44 PM »

So i've checked the 3.15V (3.4V in my DMM) taps: the pilot light comes on, heaters on V5 and V4 (pins 2 and 7) all see 3.15V.



.....  About the center tap, there is a sticker in the PT. reads as follows
- 2 x yellow = 6 V
- black 2,5 mm2 = 3,15
- green 2,5 mm2 = 0 V
- red 2,5 mm2 = 3,15 V
- 2 x red 1,5mm2 = 340 V
- green 1,5 mm2 = 0 V
- orange 1,5 mm2 = 60 V

 wich means i don't have it well connected in the picture, right? The thickest green wire on the bottom(3.15V center tap) goes to fuse instead of direct ground. I'll correct it tomorrow....


* new wiring 2.jpg (1235.47 KB, 2592x1944 - viewed 157 times.)
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wyatt
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« Reply #11 on: October 07, 2013, 10:42:16 PM »

So i've checked the 3.15V (3.4V in my DMM) taps: the pilot light comes on, heaters on V5 and V4 (pins 2 and 7) all see 3.15V.



.....  About the center tap, there is a sticker in the PT. reads as follows
- 2 x yellow = 6 V
- black 2,5 mm2 = 3,15
- green 2,5 mm2 = 0 V
- red 2,5 mm2 = 3,15 V
- 2 x red 1,5mm2 = 340 V
- green 1,5 mm2 = 0 V
- orange 1,5 mm2 = 60 V

 wich means i don't have it well connected in the picture, right? The thickest green wire on the bottom(3.15V center tap) goes to fuse instead of direct ground. I'll correct it tomorrow....

Not true.

The Filament CT (thick green) goes straight to ground.

The High Tension (high voltage) CT (thin green) goes to the  .5A HT fuse.

So, what is happening with the filament wired between V4 and V3 that you aren't seeing 3.15 on the 12AX7's?
« Last Edit: October 07, 2013, 10:45:28 PM by wyatt » Logged
parrosa
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« Reply #12 on: October 08, 2013, 06:36:51 AM »

Hi, i resoldered the two green wires. Heaters ground to ground and 340v center to fuse. My written english is not the best.... Hope the picture clarifies...

The pins 4,5 & 9 from v1, v2 and v3 read 3,4v now.

Im Göing to measure all v pins without tubes next... Or is there something else to test before?

...The diode (rectifier?) board reads 340v on each Red wire from PT secondary.
55v from another PT secondary wire to this board.
 The wire out from this board reads 507VDC.

Thanks for support onde again Wyatt !!




* IMG_20131008_114316.jpg (1297.52 KB, 2592x1944 - viewed 128 times.)
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parrosa
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« Reply #13 on: October 08, 2013, 09:06:05 AM »

So, figured out wich Pins are AC/DC  Shocked that's why i had bad readings the first time....

values without tubes:

V1
1 - 334 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 350 DC
7 - 0
8 - 0
9 - 3.2 AC

V2
1 - 340 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 350 DC
7 - 0
8 - 0
9 - 3.2 AC

V3
1 - 434 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 430 DC
7 - 0
8 - 0
9 - 3.2 AC

V4 and V5 measure pretty much the same, so:
1 - 0
2 - 3.2 AC
3 - 490 DC
4 - 490 DC
5    -37 DC
6 - 490 DC
7 - 3.2 AC
8 - 0

Comparing with the voltage chart ( www.ceriatone.com/voltage/VoltageChart.xls ), i have "expected" higher voltages on DC Pins.

Exceptions are
V4&5   Pins 1 and 8 are 0V instead of 37mV

V1 & 2 Pins 3 and 8 are 0V instead of ~1,5V

V3       Pins 3 and 8 are 0V instead of 54V

are these readings tolerable? What would be the next step? Still no burning smell, hope i'm on the right track Smiley
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wyatt
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« Reply #14 on: October 09, 2013, 10:47:04 AM »

Pin 1 on V4/V5 does NOT matter, the pin isn't connected internally. Becuase 6V6 and 6L6 don't use Pin 1, Fender used Pin 1 on the socket as a handy lug for making connections to Ground. Personally, if I built the amp, I would not connected the bias probe contact and 1ohm resistor straight to Pin 8 and left Pin 1 unconnected to anything, allowing for use of EL34 if desired. But there is nothing wrong with it as is.

But I digress...Pin 1, as it stands, is unimportant. Since it's connected directly to Pin 8...it will always show whatever Pin 8 shows.

---

Pin 5 on V4 and V5 is showing your negative bias voltage. It's in the ballpark.

---

Pin 8 on V4/V5 and Pins 3 and 8 on V1/V2/V3 are all cathodes. Just make sure all their connections are right and we'll look at them again with tubes installed.

---

But I would say it's time to hook up a speaker load install the tubes and re-measure. If everything seems good, we can begin to look at the signal path for your "no sound" issue.
« Last Edit: October 09, 2013, 10:49:19 AM by wyatt » Logged
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