pentaboost ?'s

[duck_arse]

the bushing works with an insulating washer to isolate the (LM317) tab from the heatsink, so they can be at differing potentials. the washer (used to be mica, these days sillicon) goes between tab and sink, and the bush goes through the tab from the air side. a metal screw contacting the heatsink can then pass through the sunk tab, without shorting.

[LightSoundGeometry]

the bushing works with an insulating washer to isolate the (LM317) tab from the heatsink, so they can be at differing potentials. the washer (used to be mica, these days sillicon) goes between tab and sink, and the bush goes through the tab from the air side. a metal screw contacting the heatsink can then pass through the sunk tab, without shorting.

right on. so I do need it to stop the screw from shorting. but doesnt make sense, shouldnt contact be made for transfer of heat? no one in my area carries a fastener small enough.

I guess thermal paste will work like they use on CPU's ..thats how I understood a heat sink to work ?

oh, its only for isolating it so its not same as utput voltage ..okay thanks

tayda sells heat sinks but no isolating kits or screws ...no one in my area carries this stuff especially on a level so small..go over to saint louis which is 45 mins away and there is nothing either ..they have gateway electronics but they dont carry much..its as if electronics stores for parts do not exist in brick and stone.

there is one place in a town over called fastenel which might carry micro size fasteners . the are closed on weekends

i wish I had tools here to tap my own hole..maybe I can force something into the Al with brute strength.

modify ..cant find thermal paste either ..best buy with the computer store might have some. radio shack is out and said it may not come in for weeks or months. lol ..maybe I should open a small electronics supply store in saint louis

[anotherjim]

 If the heatsink can itself be insulated from the chassis, you can omit insulation under the device. As the TO-220 317 has a live tab (it's the output terminal), you MUST insulate it from directly contacting chassis ground.
Most good electrical insulators are usually also good thermal insulators, so a special silicon pad is used (or mica if you can still get it, the one in the video looks like mica). You want good thermal conduction with electrical isolation!

If you can insulate the 'sink, you can just use thermal paste. I wouldn't use paste with a silicon pad, but I remember mica ones used with paste.

[LightSoundGeometry]

cant get it to work

dc PS is RED

1-5

-.6
2,2
1.1
-339mv
2.0mv

2n3906
-,6
2.7
2.7

[duck_arse]

put a heatsink on the LM317 anyway, doesn't need isolation while it's on the BB. M3 or 3mm screw will suit most of those bushes, if you can only get 6BA [why would you?] it will also fit. dunno what an american screw equiz would be, but 1/8" might be too big.
[edit :] use a small PK/self tapper/sheet/dunno what you callem screw to hold it together in a temporary manner.

what is the output voltage of the LM317? have you checked w/ the ohm-meter for the heater pins on that valve, and have you yet seen the heaters light up?

[bluebunny]

According to those ^^^ readings, 1.1V - heater/cathode is pin 3.  So a bit low.  And pin 5 is ground, so should be zero.  Pin 1 is the plate, so you'd expect many more volts there, otherwise this isn't going to do anything.  Where's your B+ coming from?  Can you measure that?

[LightSoundGeometry]

put a heatsink on the LM317 anyway, doesn't need isolation while it's on the BB. M3 or 3mm screw will suit most of those bushes, if you can only get 6BA [why would you?] it will also fit. dunno what an american screw equiz would be, but 1/8" might be too big.
[edit :] use a small PK/self tapper/sheet/dunno what you callem screw to hold it together in a temporary manner.

what is the output voltage of the LM317? have you checked w/ the ohm-meter for the heater pins on that valve, and have you yet seen the heaters light up?

it was like 1.24 volts exactly ..no the tubes dont light or heat up ..nothing is happening

no way I can have this set up wrong? its fairly straight forward and pretty simple set up ? 

the B+ I thought was teh 12volts on the pnp and pin 2




there is really nowhere to learn to bias a tube ..nothing on the tubes , google didnt give me anything I could relate to or follow/learn from


how do you guys learn what is what on a tube ? a mentor, school a teacher? a job? reading a book, articles etc?

[maartendh]

Datasheets

[PRR]

Take the tube out. What is the resistance from tube pin 3 to pin 5?

[amptramp]

According to the General Electric tube manual:

5672 - Power Amplifier Pentode

Filament volts - 1.25 VDC
Filament Current - 0.05 Amp
Max plate volts - 90
Max screen volts - 90

Typical Operating Conditions

Plate volts - 67.5
Screen volts - 67.5
Negative grid volts - 6.5
Plate current - 3.25 mA
Screen current - 1.1 mA
Transconductance - 650 µmhos
Load for rated output - 20,000 ohms
Power output - 0.065 watts

[anotherjim]

I'd have thought that if the filament should glow and it doesn't, yet has the required volts across it, then that filament is blown. Spec above suggests the filament is 25ohm hot -  it will be lower than that when cold.

[bluebunny]

Do check what Paul said, since the tube could be toast, but I'm still a little concerned with that oh-so-low plate voltage.  Try pulling the transistor (it's in a socket, right?) and putting a 100K resistor in its place (i.e. from 12V to pin 1).  This now turns it into the much simpler Pentaboost Mk I.  (No, really.)  What's the voltage at pin 1 now?  And more to the point (if we're lucky), how's it sound at the output jack?

[LightSoundGeometry]

Take the tube out. What is the resistance from tube pin 3 to pin 5?

o/l

one is reading 10k or so

I have an RCA one also reading 9.87 or 10 k

[bluebunny]

   

Edit:  You edited as I posted!

[LightSoundGeometry]

   

Edit:  You edited as I posted!

I have one from auntique radio supply reading 66K from 1-3 on DMM

it might be a good one?

I will have to re breadboard circuit

[LightSoundGeometry]

may I ask what the resistance from the filament to ground or pin5 is supposed to be?

and how can I measure the 6111 with a DMM similar to the 5672?

I really appreciate all the help and your time

the RCA one is measuring 11 ohms not Kilo ohms ..my bad

the one from tubes and more / antique radio supply is reading 9.5 ohms

I mis read the dmm

[LightSoundGeometry]

Do check what Paul said, since the tube could be toast, but I'm still a little concerned with that oh-so-low plate voltage.  Try pulling the transistor (it's in a socket, right?) and putting a 100K resistor in its place (i.e. from 12V to pin 1).  This now turns it into the much simpler Pentaboost Mk I.  (No, really.)  What's the voltage at pin 1 now?  And more to the point (if we're lucky), how's it sound at the output jack?

soon as I get back home I iwll reset up the BB and do this


all I could get from google was : infinite R from filament to heater = bad

so what does low low ohms mean, a short and bad? 

[bluebunny]

If you're reading a resistance between pins 1 and 3 on a 5672, then that's not right: they're not connected.  Pin 1 is the plate (anode).  Pin 3 is the +ve end of the filament/cathode.  The filament resistance (pins 3 to 5) will be as Jim suggested above: around 25 ohms hot.  So I guess 11 ohms sounds reasonable when cold.

The 6111 is a different beast entirely.  It's a twin triode with a 6.3V heater (the 5672 is a pentode with a 1.25V heater).  The heater sits between pins 3 and 6.  The datasheet suggests a similar hot resistance as the 5672.

[bluebunny]

all I could get from google was : infinite R from filament to heater = bad

so what does low low ohms mean, a short and bad?

You keep editing while I post!   

The filament has to pass current to heat up.  So if there's "infinite" resistance, then the filament isn't going to be passing anything.  It's likely broken.

Low ohms is approaching a short, I suppose you would say.  Whether it's bad or not depends on what you're measuring!  For a heater, low(ish) is OK - see the values above.

[LightSoundGeometry]

all I could get from google was : infinite R from filament to heater = bad

so what does low low ohms mean, a short and bad?

You keep editing while I post!   

The filament has to pass current to heat up.  So if there's "infinite" resistance, then the filament isn't going to be passing anything.  It's likely broken.

Low ohms is approaching a short, I suppose you would say.  Whether it's bad or not depends on what you're measuring!  For a heater, low(ish) is OK - see the values above.

I am sorry, I am going to have to take a nap lol ..I meant pins 3-5 like Paul told me to do. was a typo error on my part.

I was thinking open ..no go ..then low ohms was a short but I have no clue !

pin 1-3 heated up my DMM pretty quickly ..whatever is going on it reacted with the multimeter and caused enough heat transfer for me to feel it and even slightly smell the warmth from it.