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Welborne Labs ST70 Mod

B

Brio84

New Member
I recently purchased the new Welborne ST70 kit with the transformer upgrade. Took 6 months but got everything except the transformer (I finally purchased on from Triode Electronics.). A new chassis and output transformers were purchased from the very responsive Dynakitparts company. Alas, I only recieved a partial set of instructions from Welborne and he won't answer my pleas for a complete set.

So - is there anyone out there with the new ST70 kit that could send a copy (will gladly pay for it) of the instructions??? Help!
 
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Welcome to AK Brio84. Sorry to hear that it was misfortune that brought you here though. Everything I've heard about Welborne lately has been bad.:thumbsdn: Too bad too, because I'd like to have one of his remote control volume controls. Hopefully someone will be able to help you with the manual. Jay
 
hey-Hey!!!,
Does your set of instructions include a schematic? If it does, we'll be able to get you running with minimum fuss. Scan it, post it, and start asking questions...music to follow!
cheers,
Douglas
 
Brio84 said:
I recently purchased the new Welborne ST70 kit with the transformer upgrade. Took 6 months but got everything except the transformer (I finally purchased on from Triode Electronics.). A new chassis and output transformers were purchased from the very responsive Dynakitparts company. Alas, I only recieved a partial set of instructions from Welborne and he won't answer my pleas for a complete set.

So - is there anyone out there with the new ST70 kit that could send a copy (will gladly pay for it) of the instructions??? Help!
Click to expand...

I have the Welborne mods catalog from 2000 that had the Welborne ST-70 mod in it (the design is Alan Kimmels design). The catalog lists a schematic, parts and brief description. No PC board stuffing diagram. However, if Ron Welborne didn't change the PC board designators (printed on the board) you should be able to load the board with no problem. While I don't know for sure I assume that if you set the output stage adjustments as per the Dyna kit instructions your amplifier should work fine. Email me off line and I'll forward the pages that I have.

-T
 
Brio84 said:
I recently purchased the new Welborne ST70 kit with the transformer upgrade. Took 6 months but got everything except the transformer (I finally purchased on from Triode Electronics.). A new chassis and output transformers were purchased from the very responsive Dynakitparts company. Alas, I only recieved a partial set of instructions from Welborne and he won't answer my pleas for a complete set.

So - is there anyone out there with the new ST70 kit that could send a copy (will gladly pay for it) of the instructions??? Help!
Click to expand...

I built one of those also, but I wouldnt order anything from that guy EVER again...to many people got screwed. I thought he was an ass back when you did get what you ordered.

I will search around and see if I can find the instructions. It was one of my first projects and I believe I have written notes all over it...they were not very clear instuctions. Let me look. I dont think it has changed any, this one was from about the mid 90's or so.

Russellc
 
Thanks for the offer, greatly appreciated. Actually, I have the stuffing information and a bit of the wiring information, but it is incomplete. Also, it seems that the photos included do not agree with either the schematic or the diagrams that came with the kit. Cheers
 
Just a thought, but maybe you'd do best to forget trying to find good Welborne instructions (they may not exist, he certainly did a poor job on the instructions I got with a kit from him) and just post up some pics and questions. There are folks on here who are pretty good at electronics and might be able to help...with good pics.
 
Hello everyone, iam new to the board, hello brio84, i have the newest Welborne st-70 mod kit, and maybe i can help you with your kit if yours is a new one mod, write me at adiddelgado@hotmail.com, or just post in the board, Ron Welborne is bad news, he sells some good stuff, but no technical support at all. I also had the same problem with the kit instructions, i complete the amp with the schematic, but if you send me a photo of you project, i can help you.
 
newbie on this board, also

Pardon the legnth of this message, but I gotta vent. I ordered my mod kit from Welborne close to a year ago. I finally received delivery of everything (including power xformer and choke) from them a couple of months ago. My emails to him were rarely answered.

I also got a very incomplete set of instructions. The only thing that was included were instructions about putting together the pcb. Nothing concerning chassis wiring was included. Using the original dyna manual and a schematic for the original mod, I finally got the thing together. My emails to Ron about providing the rest of the instructions were never answered.

I am having the following problems:
1. With the tubes in place, the B+ measures about 475 v dc.
2. The new Welborne xformer emits a high-pitched buzzing which varies in pitch as the bias pots are turned up or down.
3. When turned to max, I can only get a bias reading of about .5 v dc in either channel.

Questions:
1. The new xformer has 2 primary windings. Should both be connected in parallel to the ac? There is an orange tap on one of the priamries. What for?
2. On the circuit board, the transformer has been connected in the following way - (from the left of board) red, red ; yellow, yellow(5 v filament to V5); black, black (from choke); violet (bias supply); red/yellow (ct ground); gr/wh, blu/wh (center tap of filament voltage.)
3. In all the mods for this amp, pins 1 and 8 on each output tube are connected together. Should they be on this amp also?
4. On the pcb, there is a solder pad marked "chnd." I assume this is chassis ground. Correct?
Sorry for the rant! I couldn't get any response from Ron!

Sincerely,
aliveatfive
 
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Aliveatfive wiring

Regarding your listing of the way you connected the wires, can you re-state, referring each wire to the identifier in the solder pad?

Cheers
 
OK - Here it goes:

New power transformer: 2 primaries, first is brn, blk; second is brn/wh, blk/wh. First primary is tapped with an orange wire. (not center tapped.)

Secondaries: gr, gr (with center tap gr/wh) is a 6.3 v out.
blu, blu (with center tap blu/wh) is a 6.3 v out.
red, red (with center tap r/yel) is the hi voltage out.
violet (instead of r/blu) is the bias supply.
yel, yel is the 5 v fialment supply to the rectifier.
wh, wh (wh/red center tap) is an extra 6.3 v out.

Circuit board wiring:
pad I - red (from transformer)
pad J - red (from transformer)
pad M - yel (from transformer)
pad N - yel (from transformer)
pad O - blk (from choke)
pad P - blk (from choke)
pad Q - violet (from transformer)
pad R - red/yel (from transformer) this is a ground connection
pad K - gr/wh (from transformer)
pad L - blu/wh (from transformer)

pad F - pin 8 of V6 and V8
pad D - pin 6 of V6
pad E - pin 6 of V8
pad H - B+ to output transformer

Any suggestions greatly appreciated. Thanks for the help!
 
Brio84 said:
Regarding your listing of the way you connected the wires, can you re-state, referring each wire to the identifier in the solder pad?

Cheers
Click to expand...

OK, I have located the "instructions" will get them off in the morning.

Russellc
 
Welcome to Welborn Labs customer service. I still have a remote control unit I can't get working.
 
One of the best things to do is to make the rounds of sites such as this, and clue the members in on your troubles. Eventually, this guy will either "get it" or go out of business. Free Enterprise in action.

Does anybody know anything about Roy, over at Tubes4HiFi.com? His reproduction ST-70s are really nice looking, and he appears to have made some major improvements.
 
Just to let the long-suffering know: I got in touch with the BBB website to report my trials and tribulations. They listed a new mailing address for him in Arizona. All I asked for was a decent set of instructions and a place to report problems with his products - one that will answer our questions! If I get any information, I will report it here. BTW - there is another bb (I believe it's diyaudio) which contains many posts regarding Welborne's lack of attention. If you want some sympathy, you might read the posts.
 
aliveatfive said:
Just to let the long-suffering know: I got in touch with the BBB website to report my trials and tribulations. They listed a new mailing address for him in Arizona. All I asked for was a decent set of instructions and a place to report problems with his products - one that will answer our questions! If I get any information, I will report it here. BTW - there is another bb (I believe it's diyaudio) which contains many posts regarding Welborne's lack of attention. If you want some sympathy, you might read the posts.
Click to expand...

There are probably posts at almost any audio site around. AA, here, wherever. He's been *&$%ing people for a while now.
 
Welborne ST70 Done and Working!

I just finished my Welborne ST-70 - thanks to all of you who have helped me get this project under control. also, Ron sent out updated instructions which helped a lot. After tracking down a few bad connections, it fired right up.

And - it sounds really good - very pleased with the sonics.
However, the first couple of times I turned it on there was a very transparent plume of smoke - could barely see it. It seemsw to have gone away. Second, the power supply voltage is 445V instead of the maximum of 420 VDC according to the instructons. and third, it emits a very "electronic" smell after a few minutes of operation so I only run it for 20 - 30 minutes or so. I presume thatthis is connected to the high voltage. any thoughts about why it is so high (I tried another rectifier tube - same result). Maybe the choke? Bias is perfect and both channels are exactly the same measurement.
 
Brio84 said:
... Ron sent out updated instructions which helped a lot. ...
Click to expand...

Brio84:

Since this guy seems to be such a jerk about customer service, perhaps you, and others, could post or otherwise make available the instructions, schematics etc to others that need it? Don't know if this jerk will cause grief about posting on the internet but you could share via email offline.

Just a thought.

Shelly_d
 
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