5F6A in a Baldwin Chassis

[mresistor]

Well    take me down to the shed and smack my pee pee. I am telling you   for a fact    that I was thinking of the 6,6K rating of the OT. Plain and simple.  I AM and WAS not deviating from using the PT AND choke, as we had already talked about and determined that they need to be used together. Sorry I bothered you. But there is a DELETE button, and if it's not used for deleting something you decided very shortly after posting that you don't want to say, then tell me,.    what is it for?     
 And you could have deleted your reply  as well...   then all would have been good...


I will excise the delete button from my usage,    never to use it again...  I will be a good boy and try not to post anything without thinking it totally through.   OK?   


Cool   have a nice evening 

[sluckey]

But there is a DELETE button, and if it's not used for deleting something you decided very shortly after posting that you don't want to say, then tell me,.    what is it for?

The delete button is there for you to use as you see fit. I've used the delete button. Lot's of others have too. The downside to deleting a reply comes when someone has responded to your reply. Now that response is just dangling and usually doesn't make any sense to others reading the thread. And it can be frustrating to the person that made the seemingly stupid, disconnected response. You just deleted two posts that I had replied to, so my frustration was a bit more than normal. Today that's OK.

What was even more frustrating than the fact that you deleted the replies was that you came back and tried to tell me you said something different than what you deleted. But I had quoted your original reply word for word so there was no question about what you said.

No harm done. I'll just continue to use the quote button whenever replying to your messages.
 

[mresistor]

Nope sorry - I did not try to say anything different.  If you think you can read my mind based on written words, be my guest. But, calling my integrity into question isn't really prudent. I have stated what I meant in the first deleted post, and again in my paraphrase of it. Your interpretation and subsequent post was off base and you don't seem to be able to understand that, and it is especially rude of you to not accept what I have told you.
So no harm done.  I will continue to post as I always have.

[mresistor]

Additionally, Sluckey, if you have a beef with me, put it in a PM and not here in my build post.

[sluckey]

No beef. No pms. I'll just stay out of your threads.

[mresistor]

Well  - after some time getting this thing re-configured, and a couple medical problems, I have gotten the board installed and wired up. And upon firing it up I have 425vac on the PT secondary leads to ground  at the rectifier.  I would say more but I am dead in the water until I get another bias capacitor and replace the diode and range resistor. I installed that bias diode backwards for the first time in my life. Smoke city. This board has not been easy as the layout is inverted from Hoffmans layout.


Sluckey, I  think I am going to need more than 1K on the bias tap but when I get it working again I guess I will see what the voltage range is. I have not installed a rectifier yet, obviously, and I think I'll disconnect the bias tap until I get all the other voltages on the PS rail ironed out.


I do have a 52v zener I could install on the PT secondary CT if necessary, but I am anxious to see what kind of V that choke is going to drop, or if it will even work in this configuration and not short out.   

[mresistor]

I am also waiting for a 470 ohm 3W resistor so pls disregard that sand cast one. Also I can just leave the bias range resistor out and leave the bias tap connected until I get the PS node V's sorted.

[mresistor]

OK   with a 5U4GB installed I have 505 vdc on PS node A. This is unloaded, no other tubes installed, and the bias circuit disabled. It would appear that the choke, rectifier and first PS filter caps  are dropping 350vdc in this unloaded state. I really don't know how much voltage the circuit is going to drop when all the tubes are installed and biased properly.

[mresistor]

IYes. New value will be approx. 100K.

I was thinking of a 220K to start off with ...   

[mresistor]

Well since you have blocked PMs from me 


Steve     hi how are you?  Look I don't understand why you are so worked over such a trivial thing.  Can't we let this bad water go under the bridge?Can't we be friends?  I harbor no animosity towards you.  I could use a little help with this Baldwin. I tried a 52v 50w zener on the PT CT and instead of dropping the high voltage it raised it. At the time I had one 12AY7 plugged in to get some sort of current flow on the power rail. 515 vdc is just way too high to operate at. I will have to change the first two ps filter caps to series config and bleeder strapped. I was able to sub a cap into the bias circuit and inserted a 220K range resistor and got a sweep of -25 to -40 volts, which of course willdecrease it I ever get the high voltage decreased.  I know it's not enough for the 6L6's. OK  thanks..


the zener I used is an ECG5277AK

[mresistor]

And by the way Mr. Luckey   you are punishing no one but yourself .

[HotBluePlates]

... I tried a 52v 50w zener on the PT CT and instead of dropping the high voltage it raised it. ... the zener I used is an ECG5277AK

The ___AK part is the correct type, with the zener cathode bonded to the case.  As long as that cathode is connected to chassis ground and the anode is connected to the center-tap, you should be getting voltage drop.  You'd measure that with your meter's black lead on the chassis and the red lead on the center-tap, with a reading of -52v (or a bit less since you're not drawing full current).

You're already aware of the issue of your amp's bias voltage being dependent on the reduced B+ due to the zener.

[mresistor]

HPB - thanks   the zener was bolted to the chassis near the pt. I did read a v drop of 50 volts across it. But for some reason now I have higher voltage on the pt secondary and the rectifier. It was 505 before zener and now its 515 with Zener. Strange.
I am going to change the plate filter node to two 100uf 450v caps in series with bleeders, I am worried about exceeding the 500v rating of the two 22 uf  in parallel.  Also HPB I can raise the bias range more negative by changing the bias rng resistor. I've got a 220K in it now. I was saying if I got the high voltage down the negative voltage on the bias tap will be reduced too so I would have to decrease the range resistor value to get it back up.


Really   I kind of expected this to not work out.   Proabably have to shove it into the closet and forget about it.. 

[HotBluePlates]

HPB - thanks   the zener was bolted to the chassis near the pt. I did read a v drop of 50 volts across it. But for some reason now I have higher voltage on the pt secondary and the rectifier. It was 505 before zener and now its 515 with Zener. Strange. ...

If the winding is 425vac, that implies 601vdc unloaded.  If there was a load, you might have voltage sag due to the rectifier & PT winding resistance.

I suppose it's possible that with the reduced PT voltage (375vac after 50vac zener-drop), leading to a lower unloaded voltage of 530vdc, that the current draw could be lower, so a reduced apparent voltage drop.  But it depends how much current & what was dropping it: going from ~100vdc drop to ~15vdc drop seems a little odd (though perhaps not impossible).

[mresistor]

HPB - this is so odd...   I removed the zener, and reconnected the PT CT to ground. Now I have 525 vdc at PS node A the plate supply.  I now have -40 to -60v dc on the bias circuit measured at the 220K resistors.  The bias is good enough to install some tubes but I am hesitant to do it not knowing what to expect.  It's like the zener wasn't even there. I wonder if a 50w zener needs a certain level of current to work properly?

[mresistor]

OK  update   -   I installed a couple of old 6L6 and turned it on.  I now have 447 vac at the Pt secondaries and 421 vdc on the plates.  Much better.   I now have -47 vdc on the bias swinging up to -70 vdc.
So I need to adjust the 220K bias range resistor upwards a little, to like 250K.  What a difference a couple of power tubes and some current make. 

[mresistor]

In a previous post I stated one of the bias caps smoked..  yes it did, but it was because I had a 1K bias range resistor in there by mistake and the high AC voltage exceeded that poor little 100v caps voltage rating and the plastic coating on the outside was literally burning up..    hence   smoke..    my bad..

[HotBluePlates]

OK  update   -   I installed a couple of old 6L6 and turned it on.  I now have 447 vac at the Pt secondaries and 421 vdc on the plates.  Much better.   I now have -47 vdc on the bias swinging up to -70 vdc.
So I need to adjust the 220K bias range resistor upwards a little, to like 250K.  What a difference a couple of power tubes and some current make.

This is good.  You likely already know you'll still need to reconfigure your filter caps for the full unloaded voltage (over 600vdc).

I think I had forgotten zeners need a current drawn to activate their voltage drop.  It was silly for me to forget that, since VR tubes (0C3, 5651, etc) must have a minimum current drawn through them to establish their drop voltage as well; these things are a vacuum-equivalent of a zener.

[mresistor]

Thanks for sticking with me HPB -  OK  I discovered some serious mistakes. First, using Paul Ruby's guide I discovered that the PI plate load resistors and the PI coupling caps were swapped in their positions on the layout, which I have corrected. Hope the caps weren't damaged.  Second, all the pots are wired with reverse rotation for a Marshall type chassis, tubes up.. So I've got some work to do to correct that... meanwhile.....


The amp works, although I'm sure this isn't what it's supposed to sound like. The Baldwin OT has two taps, 8 and 16 ohm. I have the 27K feedback resistor connected to the 8 ohm tap, which is pretty heavy feedback ala JTM-45. The amp has a real raspy sound and has a sort of blossoming and fading type thing going on. It does not get very loud. Should be a lot louder so there is a volume issue too. The bias is at -49v.


With a 5U4GB installed (Zener removed) the voltages on the power rail are (A) 375  (B) 343  (C) 311  (D) 235. I am surprised at this and was not expecting the voltages to come down so much. That big choke is really dropping some volts. The (D) node is too low because I have an 18K 3W on that node as I am waiting for a 10K 3W to arrive. It looks like I need to procure a GZ34 rectifier. I could use some diodes in the meantime to rectify and see how it works with higher voltages, and the voltages would be pretty near normal for a 5f6a I would think.


I'll get the pot wiring squared away for now.

[mresistor]

I redid some things and changed all the components to exactly like Hoffmans layout except for the PS rail. Pots wired up right. Went over the voltages compared to what some others have posted and every thing looks kosher to me. Still FLABBY after about 2 on the volume pots. Tried a set of 5881s  checked and rechecked bias..  still flabby as heck.  I am tending to think the OT is shot. Is it possible the OT is breaking down under load?

[mresistor]

Temporarily installed a brand new Super R OT and it sounded exactly the same. Distorted flabby nasty sounding weird decay on notes especially bass notes. Has lots of power just sounds terrible. Definitely not normal. Reconnected original OT. Will install 2x100uf caps for first filter node with bleeders. Guess the problem is on the board somewhere.

[mresistor]

Hello, I thought I would update this thread with the results, in case anyone else decides to make a bassman or similar out of a Baldwin Orgasonic' iron and chassis.
I finally got a 10k 2 watt resistor on the D power node. And I installed a 12AY7 and 5AR4 rectifier as required. Also, since the power rail can surge on start-up to well over 525 volts, I wired up the
first stage of capacitance (reservoir) like on a Super Reverb, and installed a standby switch. I uses two 100uf 450 volt caps in series to ground with the 220K bleeder resistors.
When turned on to standby the reservoir caps take appx. 10 seconds to charge up and settle, and I suppose this is due to the very large input inductor. When turned on I get
A= 400v  B= 395v C=355v and D=300v   on the power rail and even though these voltages are somewhat lower than on a real 5F6A the amp sounds pretty darn good. I have it
biased at -45v and running two 5881's at this time.
I think overall this has been a successful conversion.
I'd like to thank Sluckey and HPB and all others for the assistance.


~All the best to you folks.