[jaylevine]

Well after 3 days of hard work (including a fulll day of debugging errors), I'm up and running! The wiring is going to get cleaned up later as I've got to sort out something when Bob sends me the parts (I undid the wire wrapping when I was debugging).

Now for some Music and that warm tube glow!

[Bob2]

I'm sure you will find the Tubes4hifi amp kit to have excellent SQ.
I have a pair of MKIII's from Roy and have a lot of trouble free hours on them.
Great kits and superior sound!
All of the Tubes4hifi gear has an excellent pedigree!

[jaylevine]

Yes, I hope so

Next step is to clean up the rats nest wiring job and reapply the clear coat finish re: i marred it up before it cured while disassembling and reassembling the unit like 5 times yesterday 

I had a couple of early problems--first I mis-wired the rectifier tube which caused it to arc when i fired the unit up    Sorted that out....then checked for bias voltage and discovered I was shorting two low-voltage wires on the driver board to chassis (pushed them in too deep from the top--  )

I then had another small issue which caused the rectifier tube to arc a second time .

Anyhow got all of this sorted out about 6PM last night. Played music for two hours, went to dinner, left the unit on and upon returning around 8PM found the unit had blown the fuse.  .

Sooooo this morning rechecked all of the voltages, installed a fresh rectifier tube thinking the first may have gone south after all of the punishment I meted out during the diagnostic / initial start-up runs, installed a new fuse, re-biased the tubes......So far so good. Been humming along at moderate volume for the last 90 minutes without issue.

If another fuse pops with the new rectifier tube, Bob suggested I recheck solder joints while I'm cleaning up the wiring--he thinks it is possible heat expansion can cause a poor solder connection to weaken to the point of failure...

Quite an adventure.

[bacobits1]

I envy you even attempting the build. I'm not that talented wish I were.
Carry on, you'll get it..............enjoy.

[FullRangeMan]

Nice photos
I admire people who can make a tube amp with their own hands.

[jaylevine]

I envy you even attempting the build. I'm not that talented wish I were.
Carry on, you'll get it..............enjoy.

Thanks, but I'm not very talented myself. I am however very persistent (recall I had to take this thing apart like 5 times yesterday alone).

In my work life (technology/operations) I tended to promote 'buy vs build' with regard to the software applications I oversaw. However since entering into part-time retirement I needed something to focus my energy.

Lastly, keeping my D-SONIC M800S near just in case

[sabciu]

Yes, I hope so

Next step is to clean up the rats nest wiring job and reapply the clear coat finish re: i marred it up before it cured while disassembling and reassembling the unit like 5 times yesterday 

I had a couple of early problems--first I mis-wired the rectifier tube which caused it to arc when i fired the unit up    Sorted that out....then checked for bias voltage and discovered I was shorting two low-voltage wires on the driver board to chassis (pushed them in too deep from the top--  )

I then had another small issue which caused the rectifier tube to arc a second time .

Anyhow got all of this sorted out about 6PM last night. Played music for two hours, went to dinner, left the unit on and upon returning around 8PM found the unit had blown the fuse.  .

Sooooo this morning rechecked all of the voltages, installed a fresh rectifier tube thinking the first may have gone south after all of the punishment I meted out during the diagnostic / initial start-up runs, installed a new fuse, re-biased the tubes......So far so good. Been humming along at moderate volume for the last 90 minutes without issue.

If another fuse pops with the new rectifier tube, Bob suggested I recheck solder joints while I'm cleaning up the wiring--he thinks it is possible heat expansion can cause a poor solder connection to weaken to the point of failure...

Quite an adventure.

Wow!! Sounds like you ran across some challenges! My guess is something perhaps got hurt when you ran into your original issues, causing your fuse to blow later? Well that's just a guess. I am certain you'll sort this out with additional troubleshooting time. Both of my M-125 came up error fee, but I did take my time and even created a wiring key while going through it. With that many wires, it's a MUST to triple verify your connection.

[sabciu]

Nice photos
I admire people who can make a tube amp with their own hands.

It does require some skill and you have to be good with your hands. However, with some practice I think it's totally achievable by those that feel slightly threatened by it. There are enough YouTube videos explaining soldering and point to point connections. Practice makes perfect!!

[jaylevine]

Wow!! Sounds like you ran across some challenges! My guess is something perhaps got hurt when you ran into your original issues, causing your fuse to blow later? Well that's just a guess. I am certain you'll sort this out with additional troubleshooting time. Both of my M-125 came up error fee, but I did take my time and even created a wiring key while going through it. With that many wires, it's a MUST to triple verify your connection.

Well I'm cautiously optimistic it was the first rectifier tube that I punished re: the unit has been running continuously for close to 6 hours today without issue. I've been checking the bias every couple of hours as well and it seems very stable at .5 volts all around.

I've always subscribed to the belief that things don't happen randomly in electronics (or software for that matter)--all symptoms should repeat if all other parameters are equal. So if there was a soldering joint problem and heat expansion caused it to fail, it would have repeated by now.

Of course it could have been a voltage spike since we had storms here in Richmond VA last night, but I'm running the unit on a pretty heavy duty spike protector and these are 5 amp slow blow fuses, so I have to assume it was a sustained current draw that caused it to pop.

That leaves the only component that clearly had an issue, the first rectifier tube that I arc'd twice!

Of course I could be wrong
 

[sabciu]

Well I'm cautiously optimistic it was the first rectifier tube that I punished re: the unit has been running continuously for close to 6 hours today without issue. I've been checking the bias every couple of hours as well and it seems very stable at .5 volts all around.

I've always subscribed to the belief that things don't happen randomly in electronics (or software for that matter)--all symptoms should repeat if all other parameters are equal. So if there was a soldering joint problem and heat expansion caused it to fail, it would have repeated by now.

Of course it could have been a voltage spike since we had storms here in Richmond VA last night, but I'm running the unit on a pretty heavy duty spike protector and these are 5 amp slow blow fuses, so I have to assume it was a sustained current draw that caused it to pop.

That leaves the only component that clearly had an issue, the first rectifier tube that I arc'd twice!

Of course I could be wrong

Your spike protector may have contributed to the fuse blowing. If my memory serves me correctly, Bob doesn't recommend any type of spike protectors or Filters eithnthese Amps. There are some threads directly related to he use of filters and surge protector use with his Amps. If it blows again, you might want to try running it Direct and without a surge protector.

[jaylevine]

Your spike protector may have contributed to the fuse blowing. If my memory serves me correctly, Bob doesn't recommend any type of spike protectors or Filters eithnthese Amps. There are some threads directly related to he use of filters and surge protector use with his Amps. If it blows again, you might want to try running it Direct and without a surge protector.

Interesting, not sure how that could be; i searched for relavent threads but couldn't find anything. If you happen to have a reference please pass it along.

BTW: any thoughts on how long tubes should 'burn in' on average before being considered stable? Also tips on biasing are very welcome (i've been obsessively checking the bias like every hour and only fluctuating about .01 over the six hours it's been on).

Thanks

[sabciu]

Interesting, not sure how that could be; i searched for relavent threads but couldn't find anything. If you happen to have a reference please pass it along.

BTW: any thoughts on how long tubes should 'burn in' on average before being considered stable? Also tips on biasing are very welcome (i've been obsessively checking the bias like every hour and only fluctuating about .01 over the six hours it's been on).

Thanks

Here is a link where Bob comments on this subject http://dynacotubeaudio.forumotion.com/t2945-st-120-problems

[jk@home]

Of course it could have been a voltage spike since we had storms here in Richmond VA last night, but I'm running the unit on a pretty heavy duty spike protector and these are 5 amp slow blow fuses, so I have to assume it was a sustained current draw that caused it to pop.

I entertained the idea of building a pair of M-125 mono amps for my KEF LS50s for quite a while now.  Keep at it, you will work out the bugs, from what I have read, many folks are happy with their VTA stuff.

Anyway I'm going to laze out on the diy this time around, next month plan to drive up to Richmond (live down in VB), visit the Audio Exchange and order a Rogue Atlas Magnum. Have you had any dealing with this store?

[jaylevine]

The Rogue Atlas is a really nice unit--looked at it while I was out visiting my son in Seattle last month and even called them directly to chat about a unit. Great company with stellar reputation for customer service.  What I would have bought if I hadn't gone the kit route.

PM'd you regarding your other question.

[jaylevine]

Here is a link where Bob comments on this subject http://dynacotubeaudio.forumotion.com/t2945-st-120-problems

Thanks. He wrote me offline to explain. His concern is with cheap surge protectors that deform the AC wave form. I'm using a quality heavy duty unit from ISOBAR -- shouldn't be an issue.

[FullRangeMan]

It does require some skill and you have to be good with your hands. However, with some practice I think it's totally achievable by those that feel slightly threatened by it. There are enough YouTube videos explaining soldering and point to point connections. Practice makes perfect!!

Thanks for the encouragement, Iam not bad at soldering what I do not know is read schmatics and make the initial adjustments.

[sabciu]

Thanks. He wrote me offline to explain. His concern is with cheap surge protectors that deform the AC wave form. I'm using a quality heavy duty unit from ISOBAR -- shouldn't be an issue.

No,problem. I came across it when building mine so I figured it was at least one more thing you can look into. 

[sabciu]

Thanks for the encouragement, Iam not bad at soldering what I do not know is read schmatics and make the initial adjustments.

Then you wouldn't have any issues. Bob provides detailed written instructions and no schematic. It's written step by step informing you what connections to make next. I made a wiring list myself via an excel spreadsheet when I was building the M-125's, which I found was very helpful in keeping track of what connections I have completed.

[FullRangeMan]

Then you wouldn't have any issues. Bob provides detailed written instructions and no schematic. It's written step by step informing you what connections to make next. I made a wiring list myself via an excel spreadsheet when I was building the M-125's, which I found was very helpful in keeping track of what connections I have completed.

Thanks looks easy.

[jaylevine]

So have been enjoying the unit for over a month now. Couple of issues had to sort through, including blowing up a capacitor (my bad), had the unit rewired by Bill Gratix plus fully checked out once the cap was replaced (Bill assembles them for Bob Latino).

Latest issue was intermittent low level static sound out of right channel (independent of volume control). Bill advised after determining it was not related to the output section or my source a) swap / check out the driver tubes (they were fine), b) touch up the driver tube socket joints (I did) c) resolder the input driver board components on the right side of the board as much as possible.

Dam if he wasn't right. Static noise gone since re-soldering the input driver sockets and touching up the resistors and caps on the right hand side of the board.

Now only question is very very low level hiss out of left channel. Has been there since the beginning I think. Can only tell its there if you put your ear to the speaker; no impact on listening, can't even detectable if your ear is not right up against the speaker (not impacted to volume control).

I've read other places that this is typical of tube amps, in particular with medium to high sensitivity speakers (mine are 94db)....

Thoughts?