"PentaBoost" - 12 volt Pentode Booster using Submini 5672 tube

[frequencycentral]

Well, somehow turned a working Pentaboost into a brick and cannot figure out why!  Audio probed and racked mind but think that it's prob something to do with all the 2nd hand bits'n'pieces I used!

Figure I'll scratch this effort and try, try again!

Yeah, similar has happened to me with other projects - persevere though.

If you want to post voltages at all 5 pins of the 5672 and the 3 pins of the 317 we can compare and maybe figure it out.

I've never had a 5672 squeal though. 

[sweetwilly]

Cheers Rick, really maessed this one up so making note of lessons learned and moving on!  Definitely worth the effort tho!

[mth5044]

Ah that sucks man, sorry to hear about the trouble.

I ordered five of the subminis incase some had trouble, plus they were just too cheap to not order more then one.

I hope you get your problems solved out before the big twincaster build! 

[frequencycentral]

sweetwilly, you really should debug though........don't waste your efforts so far, I bet it's something really simple. Post your voltages!

[frequencycentral]

Here's my 5672 voltages anyway, could be useful for someone sometime:

Pin 1: 4.24v
Pin 2: 7.72v
Pin 3: 1.25v
Pin 4: -0.18v
Pin 5: 0.004v

[sweetwilly]

Will do Rick.  Honestly, I rushed my first effort, poorly planned the wiring and re-used a lot of pieces.  Have rebuilt, much neater this time, but still no action.

My voltages are WAY out form yours and the fact that Pin 5 is 12v kind of tells me I made a slight mistake somewhere!

Will look into it tomorrow - definitely not giving up!

[frequencycentral]

Will do Rick.  Honestly, I rushed my first effort, poorly planned the wiring and re-used a lot of pieces.  Have rebuilt, much neater this time, but still no action.

My voltages are WAY out form yours and the fact that Pin 5 is 12v kind of tells me I made a slight mistake somewhere!

Will look into it tomorrow - definitely not giving up!

Yeah 12 volts to the heater won't be good for it!

[sweetwilly]

Yup.  My jumper from Pin 5 to ground overstepped by a hole! 

Reckon the tube's dead Rick, or could it be something I'm missing? Voltages are

1 - 0.00
2 - 10.94
3 - 1.20
4 - -0.01
5 - 0.00

Thanks!

[frequencycentral]

Yup.  My jumper from Pin 5 to ground overstepped by a hole! 

Reckon the tube's dead Rick, or could it be something I'm missing? Voltages are

1 - 0.00
2 - 10.94
3 - 1.20
4 - -0.01
5 - 0.00

Thanks!

Don't give up on the tube yet - they're pretty tough. Have you got a short to ground at pin 1? Are you sure the resistor between pin 2 and +ve is the right value?

[sweetwilly]

Just to check, I swapped ol' squealy in to see what it's voltages are like.

Think I must have a short to ground somewhere as still nowt on Pin 1.  Pin 2 is only 3.12 on this one though.  FWIW - squealy glows, the previous one didn't (well it did, very brightly, when I had 12v going to the heater!).  Don't think this is of any consequence, just interesting,

[frequencycentral]

I accidentaly put 12 volts through a 6111's heater recently (6.3 volt heater that one) - it survived though. Do you have a breadboard? Worth having one just to use as a test rig to check things. The small ones are a couple of quid at Maplin.

Keep me posted!

[sweetwilly]

  I know, quite ashamed I don't have one really. 

Sorted the short out - found a tiny solder bridge under the magnifying glass. 

Just probing and found at least 1 dodgy solder.  Will keep at it as long as the wife allows!

[sweetwilly]

Perseverance has paid off - I'm as close to your voltages as I think I will get and it's sounding sweet!  Another red face needed here -  as this tube is behaving like the 1st - even though it's a different brand.  Have you found them to be quite microphonic or have I just stumbled across a couple by coincidence?  Thinking the squeal could be my "clean" power supply not being as clean as it could be.  It's only noticeable when not playing and I can't think of anytime I'd have a boost on while not playing so don't see it as a huge problem!

Will try to figure out how to post sound clips tomorrow and will post some pics - my best effort at lead dress to date and I'm quite proud!

[mth5044]

Glad to hear its working. Maybe you should invest in a 1spot 12v adapter? I've never had the 12v, but I have 3 9v's and they are all clean and reliable. Especially if you are going to build the twincaster and use 12v's. Plus I think they give out 1200mA so thats plenty enough.

Just a suggestion  Keep up the goodwork!

[sweetwilly]

Here are my working (with a slight squeal!) voltages.

1 - 3.19
2 - 6.21
3 - 1.25
4 - -0.01
5 - 0.00

Just waiting on my battery to charge and will post some pics. 

Thanks for everyone's help and encouragement!

[frequencycentral]

Perseverance has paid off - I'm as close to your voltages as I think I will get and it's sounding sweet!  Another red face needed here -  as this tube is behaving like the 1st - even though it's a different brand.  Have you found them to be quite microphonic or have I just stumbled across a couple by coincidence?  Thinking the squeal could be my "clean" power supply not being as clean as it could be.  It's only noticeable when not playing and I can't think of anytime I'd have a boost on while not playing so don't see it as a huge problem!

Will try to figure out how to post sound clips tomorrow and will post some pics - my best effort at lead dress to date and I'm quite proud!

I ve never had squealing with 5672, and I've breadboarded lots of ideas with them recently. The do go 'ding' if I tap them with my fingernail though. In my PentaDriver I put foam padding round them.

The squealing could be a power supply issue, or a solder bridge. Did you try running it from a 9 volt battery to see if the squeal goes away?

Glad you got it working though - I bet the wife is pleased too!

Watch out for my 'Red Star Drive' coming up soon - another 5672 clipping device................


EDIT: I use this power supply: http://www.maplin.co.uk/Module.aspx?ModuleNo=32746

[sweetwilly]

OK, after clipping a battery snap in and hearing no squeal I figured it was either the power supply or the hole in the wall.  Turns out to be the hole in the wall!  Tried another outlet and get no hum, squeal or noise! 

SWEET!!!!

[mth5044]

Ah the sweet smell of success.

Congrats.

[sweetwilly]

The squeal never went away    just wasn't noticeable without the amplification it gets from the rest of the gang.  This thing drives tubes so well that I won't be giving up on it.  I was going to give this to a mate that makes pretty messed up experimental stuff, so the squeal may appeal!

Mark 2 might even get a prettier enclosure and all!

[Renegadrian]

YEAH, don't give up, I know it gets you in a bad mood but hey when you get it working correctly it's like heaven...

Red Star Drive - what is that? Mate, you ain't tired of tubes yet?!  (hope you never will!!!)