Upgrade Dcavers

[shooter]

original build here
http://el34world.com/Forum/index.php?topic=24695.0

My new PT showed up!!
Time for an upgrade
DoubleCavers currently has 3 separate PA’s each with it’s own PS, 2 wall plugs, 2 power switches, 3 boxes………….. 
I’d like to replace the ‘70s amp with 2 Velleman 8060 kit mono’s same amp I’m using for the center channel but that will have to be phase II after I sell some furniture. 

For now I’ll work on downsizing to single PS, plug, switch…….
Scribble goal is unregulated +/- ~~38vdc using same design I stole for 1st ps.  Hoping to just swap in the extra 9 lbs of iron to get better than guessing #’s.  this phase the ‘70s amp might die, (got spares:) since it only runs on 1 rail @ ~+30vdc. ( keepin it 1 rail!)  The bipolars are marked with #’s I haven’t been able to track down so I’m betting RCA was conservative in design   

[shooter]

took some time n made a box  (~ 16 X 7 X 6)
As I was stripping down the old PS I realized the rectifier wasn't gonna cut it, so off webn  for bolt in diodes

do have a question;
the total PT output is 60VAC (30-0-30) @ 10.4A, assuming ~~ 6-8A continuous with instantaneous spikes to ~~ 15A +

will 15-20A sinked diodes work?
If something blows & the fuse doesn't wake up fast enough I'd prefer the diode to loose over the tranny.

thanks
dave

[PRR]

> will 15-20A sinked diodes work?

Pick your rectifiers higher than the transformer rating, and round-up as long as the price does not soar.

25A on a  10A winding would be fine. 15A may be fine. Especially if you treat it like you own it, don't short the speakers, don't beat it past 100% distortion.

Your average current on clean speech/music is likely to be closer to 1 Amp. Bench-testing maximum sine-wave in 8 Ohms will be like 3.3 Amps. If you ever get 10A in winding or rectifier, something has already gone wrong.

[shooter]

something has already gone wrong.

Thank you!
and ya it will be "my own"
I'm starting the dive on your fuse article
found a 16A 1200/1400 piv bolt down from Vishay VS 16series

sellin some scrap metal!

[shooter]

I  I could get things done faster on the web with my commodore 128 9600 modem in the 90's 

gave up, drilled n cut.
Upgrading the PS to compensate for inrush I
1st pass for a turret pcb 

[shooter]

Logic check if possible;

Building this PS, minor hang-up on the inrush circuit

I’m not using the mute so I reduced to fig 1
Found a site with all in one that’s NOT zonbay
But the 43v Zener available = 39.5v
The relay spec shows must latch 38.5v
Modified to fig 2

Is the logic correct, by adding **,   RL1 = 39.5 + ** Vdrop?


The TI datasheet says PS is  +/-72vdc unregulated, my math shows 72/2 = 36Vcc.
I’m kinda hung why use 48v relay instead of 24v relay with matching Zener to = 36vcc?

Thanks

Dave

[PRR]

Why do you think you need inrush current control??

I bet the lights hardly flicker when you turn it on.

Of the making of many frills, there is no end. And that TI plan is extremely frilly.

[shooter]

I'd agree but I don't know enough 
my main concern is all the scary stuff I read about LARGE inductive kick and thinking I don't want to throw away another Benjamin for a new PT.  I can deal with nuisance fuse blows.

the 1st version had no protection, same 2ndary, but much less load.  this version has 4X the old load 

guess it'll be a $40 experimental circuit 

thanks

[shooter]

Got some mechanical work done
need to isolate the heat sinks for the diodes

[PRR]

Turn-on "surge" won't hurt a transformer. It will take many minutes to hot-up that huge lump.

[shooter]

Ok, I'm switching to no step-start, found a 35A bridge instead of single diodes, way less headache for layout/noise coupling.

gonna start with 12 - 15A primary fusing.   temping in a couple 8A/rail knife fuses and see if I actually have to do math 

hopefully by this time next week I have sound without smoke 

[shooter]

……many weeks later……

Used a new site for me, FutureTec (sp?) Based in Australia,  ships from Bangkok, my box in 3weeks
The up-side, 3lb box 4$US 

Un-loaded I’m 10vdc high, ballpark guessing ~~ 1.5A per mono.  If tests pass I’ll gut my original for a 3rd mono.  That should get me to too cold to play
workin on the Amp layout n final soldering, rattlin teeth in a week 

[shooter]

minor progress;

[shooter]

more minor;
inputs are wired 'sept center, testing as stereo 1st

I couldn't recall the ugly roof style I keep seeing , wiki had it;
Mansard

[shooter]

Mechanical n soldering done!
power-on testing tomorrow while the street's at work unless the Earth thumping trucks fire up, then I'll be putting rounds down field, helping the Geologists with their mapping 

[Ed_Chambley]

Doesn't look like a geetar amp.  I am bad about sharing photos.  Working on a Double single ended stereo KT88, 6SN7 PI.  I found the problem with my Marantz 7.  As always, a wiring error and had to cut the gain a little on the phono stage.  It is triode connected with a 270ohm.  I was gifted the transformers.  The PT I was given puts out with 2 rectifiers, 521 plate and I fired it up with some real =C=.  The 6sn7 is really a RCA 5690, which is a 6sn7 wearing dark Foster Grants.  Yes, it is cool.  Right now I am easily getting 30+ watts driving Altec Lancing (heatkit as101) same a voice of theater.  Almico 15 and horns.


So, I will have a Marantz 7 Pre and I will put it into a wooden box as it should be.  I did not add the eq in this build.


I really like the sound of the amp in Triode as the vocals with the Altec horms are great.  I had hoped I could get it to move bass, but I revised the plan to use a yamaha EQ, active crossover set at 150Hz and a nice old Crown amp only for 150Hz - 35 Hz.  Cleaned up the top end and is extremely open and airy.


Couple of kinks to work out, but it is sounding really nice with a 76 Marantz Table.  One kink is I decided I wanted a attenuator, but motor driven for a remote, so I will have it back open.  Hell, I have everything back open at times.  Anyway, the motor needs 9VDC.  Tried a battery and it works great, so I need to find a reguated 9 volts somewhere r said another way, I need to drop and requlate 9 VDC for the motor.


I have each tube fixed bias right now.  Seems the hifi guys are recommending this.  I tried a cathode bias too, I cannot tell a difference in sound, some say tubes last longer this way, but my 1960 Leslie with all original tubes seems to have done well.


For the first time, I am able to take some time.  It can easily replace 2 little monoblocks I have now, but I am waiting to get it all together until I am satisfied before I replace the units I now have.  This will be the first time I have ever been able to wait.


Of course, when you are completed you need to place Ted Nugents Double wide gonzo on the platter and crank it full up.

[shooter]

This will be the first time I have ever been able to wait.

now that ever day is Saturday, I've gained the ability to wait 
I LOVE my 417!!  The original folded horn box has been repurposed as a skeet thrower stand.  The smaller PA closed back box works well, do need to re-build the Altec L-pad the 15" seems to get a little squirrely around 7k.  the cheapy Klips bookshelf hold their own well in the barn to balance out the Altec center.

I still have a PCB tube Marantz 7 pre, although I cobbled it up as a fender something last time it got used, easy enough to get back.
Before here I was mostly a Digital geek, but there has always been something we called a tube in every system just so I wouldn't get complacent 

don't tell anyone, but I like ANY well done music, especially where there's orchestrated sound behind the band, more complex musical sound.
BUT, I always play the same 2 songs (not complex, but rhythmic :) for a new build test;
1.) Uncle Kracker's Good to be me
2.) Nappy Roots Good day

my default music is country, new, old, subjective 

I'm an odd nut, I didn't quit liking music (well except the 80's stuff :) I made it to about when the Lumineers hit big and finally gave up 

[Ed_Chambley]

Well test as you will.  I built the Marantz 7 point style almost.  I have looked at some of the "phono" PCB called Marantz 7 and found one which is almost the same.  Found a website where a guy made a couple of changes to get it to perform a bit better, However, I another freind ordered one already built.  Modern looking thing.  We A/B them and as always you can hear a little difference, but it still sounded really nice.


We all have different test.  Back when JBL made their 4312 Studio Monitors (Late 70"s) they released a test audio cassette, LP and CD.  I still have the LP and it is a great test, but I still prefer this instrumnetal.

[shooter]

I am bad about sharing photos.

When I was taking other folks teens rockclimbing, they would all ask to see pics of my climbs, I'd simply stand up, turn my back to them and ask, really 
In 20yrs, there might be 2 pics of me on the rocks 

powered up, BAAAAAAAAABAAAAAABBBAAAAAAA, powered down.  poking n proding I found my 100ohm 25w ground lift was 10K
jumped for test baaaaaaaaaaaaaabbaaaaaaaaaaaaaaaaaba, powered down
figured out the boards n chassis were K's apart, gator clipped n 
volume pot must be funky starts full vol, quiet in the middle then full at other end 
prolly what I get for not testing used junk before using 
dead quiet, bias good now, +/- 42vdc, meter shows ripple at @ 20mV quick check
fix grounds and new pot should be in the can, back to geetar stuff

[shooter]

1hr 90% some of the sweetest sounds, clear crisp, gave mw shivers 
went to check temp n watched as R16 n T4 flamed out in mini splendor 
the aluminum was too hot to touch didn't have thermometer on it

they both set basically in full contact with R19 5watter and I am running +/- 3vdc over max and didn't check input signal amplitude sooo.....
duct-work tomorrow, car Wednesday......
putting a parts list together 
 

[shooter]

got out the '82 transistor book, found NTE128/129 as big bro's to the BC547/557
still lookin for the cool finned hats 

figure might as well beef up the cheap stuff n see.  I'll re-mount the 5w'r "off" board.  Gonna leave the diode and Resistors the same for now as po' boy scarifiers 

[shooter]

back at it, from the PS side 1st.
2hrs trying to find linear voltage regulator 35vdc 10A 
must be doing something wrong 

did find this, but the price for 2 is real scary

 http://www.belleson.com/download/Superpower_datasheet.pdf

I can't figure out if it's a linear VR, or Pulsed VR 

thanks
dave

[shooter]

wondering if the 2 transistors should be both NPN (2n2905 is pnp)
I'm seeing them as a Darlington pair.

so drafting error, or I gotta go back n read more 

[PRR]

https://www.google.com/search?client=firefox-b-1-d&q=szlaki+transistor

[shooter]

wow, thanks, I think 
still reading why, that configuation musta been on a Friday class I missed 

[shooter]

Got a +/- lm317 337 3A kit coming, scrounged 1st pass and found Mj11011/12 Darlington's, got a big bag of mixed TO3's but I'm not up for attic diving today.
From the read, I'm almost comfortable thinking they work in place of the szlaki

aiming for each rail;
Max 50vdc in
Min  45vdc in
Min 35vdc out
Max 38vdc out
8A fused current