It is currently Mon Mar 16, 2020 8:55 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 56 posts ]  Go to page Previous  1, 2, 3, 4
Go to page Previous  1, 2, 3, 4
Author Message
Post subject: Re: Home made 6G15 issue with voltage
Posted: Sun Jun 29, 2014 12:28 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Sat Jul 03, 2010 2:18 pm
Posts: 6544
I know this is going to sound silly, but is that 100k-ohm resistor tied to the 2.2meg-ohm one = brown-black-yellow-gold?

Thanks!


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Home made 6G15 issue with voltage
Posted: Sun Jun 29, 2014 12:54 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
The cable shielding (negative wire) is grounded, but either the input negative or the output negative of the tank itself, or both, should not be grounded. It still seems to me that you have a ground issue, meaning that something that should be grounded is not grounded, or something that should not be grounded, is grounded.

What is the number on your tank? Something like 4EB3C1B, the second and third digits tell the grounding scheme of the tank.

With everything else connected in the circuit, disconnect your reverb tank and remeasure the voltage that was low.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Sun Jun 29, 2014 1:03 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
BMW2002Ti wrote:
I know this is going to sound silly, but is that 100k-ohm resistor tied to the 2.2meg-ohm one = brown-black-yellow-gold?

Thanks!



Yes


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Mon Jun 30, 2014 12:26 pm
Offline
Hobbyist
Hobbyist

Joined: Mon Apr 07, 2014 5:53 am
Posts: 32
Stratele, yes it is a 100k resistor (like on the specs).
Shimmilou, ok you r right : I'm gonna review all my wirings and make a mapping of what is connected and where and with what.
My godness ... let's go
;)


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Mon Jun 30, 2014 3:01 pm
Offline
Amateur
Amateur

Joined: Sun Jul 22, 2007 9:29 am
Posts: 139
What are you making the measurement with?

If it's a scope your expected voltage would be aprox +60 Vdc
(because it has a 1 meg ohm input impedance, or a cheap DVM with 1 Mohm input z).

Your making a measurement -
putting 1 meg across the 2.2 Meg resistor.
and the B+ is aprox +250 Vdc.

If you do the math, +60 V is correct,
with 1Mohm z input to scope.


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Wed Jul 02, 2014 11:38 pm
Offline
Professional Musician
Professional Musician

Joined: Fri Jun 26, 2009 6:53 pm
Posts: 2252
Location: Harvard IL
Checked my Weber 5G15 tonight(swappin' the power tube). The Fluke 87(10meg input impedance) read 134VDC at the 2.2M junction that you are specifying. The wall voltage is 125VAC right now, so the B+ is 309VDC. The resistor needs to be a good 5% one,IMHO. HTH, Art

_________________
None of Us are free, if One of Us is chained !


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Thu Jul 03, 2014 7:21 am
Offline
Amateur
Amateur

Joined: Sun Jul 22, 2007 9:29 am
Posts: 139
With the Fluke 87, 10 Mohm input z the math comes out to measuring 139 V at the junction of the 2.2 Mohm resistors. Good measurement. Nothing should be wrong with the circuit, using 309 vdc as the B+ voltage.

The parallel ohms is aprox 1.8 Meg, with the Fluke 87 across the 2.2 Meg ohm R,
and solving for voltage divider node V = 139V.

At the node the Vdc is actually 1/2 of B+, or 154 V dc, the Fluke meter, which is a great meter to use, is still loading the circuit test point. They just label schematics that way.


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Thu Aug 21, 2014 5:34 am
Offline
Hobbyist
Hobbyist

Joined: Mon Apr 07, 2014 5:53 am
Posts: 32
Hi guys,

I put this project on hold during my holidays.
I'm back on it with a fresher eye.

First, many thanks for you messages and interest.
This project is frustrating me. ;)


Here is my last diagnosis :
- The 6G15 let the sound go from the guitar to the amp.
- But no reverb is added.
- When I tap the reverb tank, the echo is heard into the amp (so the output from the tank to the amp is working).
- I changed the OT for a new one (same model) because I thought it was bad (no signal into the reverb tank) : did nothing
- I tried to measure the input from the OT to the RCA plug (tank input) : I can't find any signal, even when I play a chord.
- When I check for voltages on the points with and orange circle around (see attached pic - layout from triode, best pic with colors), I have a good voltage but I can also hear like a sizzling when I put the probe on the contacts.
- Speaking about the 60V instead of 120V issue, I'm doing my measures with a simple and typical multimeter (yellow Velleman I think).
- All other measures (except the 60V instead of 120V) are ok, within the tolerance range +-20%


Thanks again for your suggestions.

Vincent

Image


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Thu Aug 21, 2014 6:02 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Welcome back

How do you take these measurements ? Give all details , meter , scale ....

"
- I tried to measure the input from the OT to the RCA plug (tank input) : I can't find any signal, even when I play a chord. "


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Thu Aug 21, 2014 7:06 am
Offline
Hobbyist
Hobbyist

Joined: Mon Apr 07, 2014 5:53 am
Posts: 32
Hi

Thanks

Well taking classical voltage measurements is ok : ground on chassis then red probe on the point. Playing with the scales to make my measurement readable (20V if i'm looking for something max=20V etc ...).
I know how to measure ALT vs CONT.

But taking the measure on the tank input is the underbelly of my approach : I put the red probe on the RCA entry or on the OT green wire. Then I play with the scales of my multimeter to see if something is showing up.
Nothing. Zero.

I can take a picture of this measure in a few hours.

Thanks
Vincent


Top
Profile
Post subject: Re: Home made 6G15 issue with voltage
Posted: Thu Aug 21, 2014 1:08 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
Sorry this not a answer, I would have liked more precision.

For reading what happen wit the reverb transformer

1- Put you voltmeter on AC scale , not DC

2- Put probes on Primary side of Reverb Transformer , not at ground

3- Play guitar on send an audio signal . What do you read ? . Try AC low scale if needed , Dwell is a volume , use it

4- If you don't read something , problem is before reverb Transformer


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 56 posts ]  Go to page Previous  1, 2, 3, 4
Go to page Previous  1, 2, 3, 4

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: