Vintage blue line svt help

[guitarfinder]

Firstly, I am an amp hobbyist and love refurbishing vintage gear.
I know this era of svt is difficult and I have searched much of the resources available here. Much appreciated!!
I have followed the schematics and info available here but I am having issues with the terminal strip at the power (120v) input.
I foolishly have tried several combinations, my pride is gone and I would truly appreciate help.
Here is the current mess,
Thx in advance

 

[agedhorse]

Now you have a mess to undo and sort out before properly fixing it (including abysmal solder joints)

You will need to go back to the schematic to study how it’s SUPPOSED to be as a first step.

They are not difficult to work on for a qualified service tech.

 

[guitarfinder]

Thanks for the reply, much appreciated.

 

[Wasnex]

That is pretty messy alright. I suspect the confusion may be because the amp appears to have the dual voltage (120V/240V) transformer.

The 74 6550 schematic (attached) is what I would use as a reference, but some of the connections may not match those in your amp. I suggest reviewing the schematic and documenting what is going on in your amp (draw it out). Post the drawing here and we will try and help.

Here is an early blueline with 120V transformer. This image is fairly high res, so you should be able to zoom in on the terminal strip, but it probably won't help very much.

Wiring with the dual voltage transformer is more complicated. You have to consider how your specific amp is wired because the molex connections (P1 and P2) vary across different generations of amps. Also, the color codes on the transformer wires can vary. The coding on your PT's primary may match the Heyboer SVT PT diagram:

 

[Wasnex]

If you have access to a good tube tech, probably best to ask them to do the work.

 

[guitarfinder]

That is pretty messy alright. I suspect the confusion may be because the amp appears to have the dual voltage (120V/240V) transformer.

The 74 6550 schematic (attached) is what I would use as a reference, but some of the connections may not match those in your amp. I suggest reviewing the schematic and documenting what is going on in your amp (draw it out). Post the drawing here and we will try and help.

Here is an early blueline with 120V transformer. This image is fairly high res, so you should be able to zoom in on the terminal strip, but it probably won't help very much.
View attachment 7436143

Wiring with the dual voltage transformer is more complicated. You have to consider how your specific amp is wired because the molex connections (P1 and P2) vary across different generations of amps. Also, the color codes on the transformer wires can vary. The coding on your PT's primary may match the Heyboer SVT PT diagram:
View attachment 7436150

 

[guitarfinder]

Many thanks, I have been looking at schematics and diagrams. They seem to vary a lot, the terminal strip and molex connector are honestly confusing me a bit.
As I study other configurations they differ a lot... again thank you

 

[bass player 53]

If you’re still determined (not recommended), or you want to simply know more, there are several YouTube videos demonstrating repair.

Google Search

 

[guitarfinder]

If you’re still determined (not recommended), or you want to simply know more, there are several YouTube videos demonstrating repair.

Google Search

Thank you, I am determined even though I realize the possible consequences. I understand high voltage and safety. I have accomplished several other repairs on vintage amplifiers. As we all know this is a different beast. Much appreciated.

 

[agedhorse]

Thank you, I am determined even though I realize the possible consequences. I understand high voltage and safety. I have accomplished several other repairs on vintage amplifiers. As we all know this is a different beast. Much appreciated.

The more you damage things (especially using the trial and error method of screwing things up), you may find that it becomes less worth repairing properly. Even more-so if you damage the power transformer in the process.

 

[guitarfinder]

Yes, I am aware.
I have reached out because I wish not to continue with trial and error. I know better but did it anyway (yes very foolish)
To be clear there was one attempt.
Appreciate the advice.
Thank you

 

[Wasnex]

I have been looking at schematics and diagrams. They seem to vary a lot

Exactly why you need to draw out the connections in your amp. Also why I can't just tell you how to do it.

Here is an example of what I mean:

This is using the 74 schematic I provided earlier in the thread:

This is from the 69 preamp and 70 power amp schematic.

Your amp may not look exactly like either of these.

 

[guitarfinder]

Very much appreciated, thank you!!
I'll check these out.
Super helpful Thanks!!

 

[micguy]

If you have access to a good tube tech, probably best to ask them to do the work.

or have a friend standing by, ready to dial 911 at the appropriate moment. To survive working on a tube amp, you have to be right at every move. To die from it, you only need to make one mistake.

I made one mistake - 760 volts arm to arm. I was lucky, and survived. You may not be as lucky.

 

[agedhorse]

or have a friend standing by, ready to dial 911 at the appropriate moment. To survive working on a tube amp, you have to be right at every move. To die from it, you only need to make one mistake.

I made one mistake - 760 volts arm to arm. I was lucky, and survived. You may not be as lucky.

And it really hurts while that happens too.

 

[agedhorse]

Yes, I am aware.
I have reached out because I wish not to continue with trial and error. I know better but did it anyway (yes very foolish)
To be clear there was one attempt.
Appreciate the advice.
Thank you

Once you start screwing with the wiring, you don't know what other mistakes you may have caused in your single attempt.

In my shop, this automatically adds to the cost of repair due to all of the additional verification and corrections necessary to then correctly do the repair itself. Hopefully you didn't damage the transformer with an incorrect connection. Not doing so is dangerous to the tech too.

Since there are multiple versions of his amp and transformer, guessing is stupid at best and dangerous as hell otherwise.

 

[guitarfinder]

Appreciate your insight
Thank you

 

[beans-on-toast]

The soldering is a mess as was mentioned. This needs to be fixed properly. A variable temperature soldering iron is needed, solder flux, solder remover wick.

You need to identify which revision you have. There are date codes on some components. Then find the correct schematic. There are several variations of the power input wiring depending on the SVT revision.

Here’s some reference notes for a ‘71. Whatever you do, don’t just accept and copy it without understanding what you are doing. Take it to a tech.

 

[guitarfinder]

Thank you for taking the time to reply. Very much appreciated, as I look through schematics and images. I see many different configurations.
Some have the neutral to the strip, some have the hot(black). PT connections vary as well. I think I am having the most trouble with the smaller wire connections from the transformer that supplies the 6.3v. One set solid blue/black and one set black-white and blue-white and how they connect to the strip and molex. in addition some have an external fuse and some don't.
Yes this is new territory but I have some experience. I understand the dangers of high voltage. I use a variac so I am confidant the pt is fine from my first and yes (stupid) attempt. I am committed to learning and understanding this circuit. Thanks to all for any help and the concern. I am grateful.

 

[agedhorse]

Thank you for taking the time to reply. Very much appreciated, as I look through schematics and images. I see many different configurations.
Some have the neutral to the strip, some have the hot(black). PT connections vary as well. I think I am having the most trouble with the smaller wire connections from the transformer that supplies the 6.3v. One set solid blue/black and one set black-white and blue-white and how they connect to the strip and molex. in addition some have an external fuse and some don't.
Yes this is new territory but I have some experience. I understand the dangers of high voltage. I use a variac so I am confidant the pt is fine from my first and yes (stupid) attempt. I am committed to learning and understanding this circuit. Thanks to all for any help and the concern. I am grateful.

Holy crap dude, you need to step away from the amp and seek more professional help before you hurt yourself. It’s now clear that you have absolutely no clue what you are even looking at.

You are calling the 120/240 primary wires 6.3 volt secondary wires. First, those colors are some of the standard primary wiring colors and second, there are only 2 wires for the 6.3V secondary.

Seriously, stop screwing around before you hurt yourself, there are wires on the secondary that can fairly easily kill you (over 700v peak) if you misidentify them and do something (even more) stupid. What you are doing is dangerous.