the Poor Man 660 support thread

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the Edcor package is a steal, thanks to codered.
even incl. the customs I had to pay. no joke.

another good news:
will be on vacation with my family for a week - without internet access.

Poor Man packages are all shipped, and I will enjoy this week without you :green: :green: :green:

see you next week :thumb:
 
[quote author="no-fi"]
you probably realise I meant the farnell part, right?
[/quote]
I didn't, and I can't get their site to load and show me data ATM.
I was asking about the capacitors ripple current.

A capacitor's ripple current rating, for an electrolytic cap, is a rating of something the cap can stand. Essentially looking at the current continually going in and out through the cap's ESR gives you an idea of how much power is dissipated in the cap. too much than the cap can handle, and you get an unhappy cap...

Now, these caps we're talking about have a ripple current rating of about 1.4A.... which might be a bit below the amount of ripple current they'll experience in this design.... which will be 6A, from what I've read on the heater current requirements.
Click to expand...

This seems to have some bearing; did you consider the temperature factor? Ripple capacity would still be low at best case. I'm not at all sure if frequency has any significant bearing; I see 100kHz is a ratings standard, but I don't really know what that translates into. Assume it relates to a higher ESR reference, which would certainly affect temp.

http://sound.westhost.com/power-supplies.htm#ripple
 
hey!

frequency doesn't make much difference.

some caps have ripple current specced at both 120Hz and 100k, and the difference is usually around 10% (can't remember what direction the difference is in, but... because low frequency ripple isn't something I have to deal with normally)

I'm not an expert on the boundaries of ripple current (I always just try to stay under with my switchmode designs) but I guess operating temperature will also effect the amount of ripple, since from what I understand, it's the heating effect through the ESR that is the damaging factor with high ripple current.

though isn't part of the problem that the poorman (especially a 670) is going to get pretty hot inside anyway??


At the end of the day, its no biggie - you CAN get caps that will take 6A of ripple, mount them to the chassis, and replace the parts on the board.... I was just wondering if what I suspected as a problem will actually be one, or not....
:grin:
 
regarding the LM317/LM337 section of the PSU (wich dosent show on the schemo) - what would be the curent draw for this part of the circuit?
the -17V is for tube bias,im guessing not too many mA here...
+/- 15V would be for the bypass relays?so for a stereo unit (4 relays)about 100mA ?what else?

im asking to know if they can live with smaller heatsinks...
 
[quote author="mich"]regarding the LM317/LM337 section of the PSU (wich dosent show on the schemo) - what would be the curent draw for this part of the circuit?
the -17V is for tube bias,im guessing not too many mA here...
+/- 15V would be for the bypass relays?so for a stereo unit (4 relays)about 100mA ?what else?

im asking to know if they can live with smaller heatsinks...[/quote]

The +17 (or other adjustment) is for.....whatever, so up to you to decide.
 
[quote author="mich"]regarding the LM317/LM337 section of the PSU (wich dosent show on the schemo) - what would be the curent draw for this part of the circuit?
the -17V is for tube bias,im guessing not too many mA here...
+/- 15V would be for the bypass relays?so for a stereo unit (4 relays)about 100mA ?what else?

im asking to know if they can live with smaller heatsinks...[/quote]

The transformer we used in the prototype provides 15V/1mA for each section. I used the positive rail for the 12V relays and lamps. I recommend to take the heatsinks as suggested in the BOM, since there is a voltage drop of at least 3V, that causes the LM317 to get quite warm.
regards
Bernd
 
emrr wrote:

The +17 (or other adjustment) is for.....whatever
Click to expand...

- No comprendo.... :roll:


emrr wrote:

so up to you to decide.
Click to expand...

- This i understand easy.


O.k , stick to the plan.after all that buying, a couple more heatsinks wont kill me... :guinness:
 
[quote author="mich"]emrr wrote:

The +17 (or other adjustment) is for.....whatever
Click to expand...

- No comprendo.... :roll:
[/quote]

Get Two more VU Meters, purchase JLMs VU Meter Buffer add a DPDT switch and toggle between the input and output of unit using the +17V

So each channel will have a GR meter and an input/output meter too.

you need the -17V for Bias but to get -17V you will also need a +17V, the +17V isn't needed for the circuit so its just there to use for whatever enhancements you want .. LEDs, VU meter BUffer, anything.......
 
hey guys

this is more of a theory question but relates directly to the PM.

if you have an input transformer with a CT on the secondary but the circuit doesn't use the CT -- can you just disregard the transformers secondary CT and not use it and all will be fine?

Its painfully obvious why I'm asking this
 
Short answer in regards to the Edcors appears to be yes. And a unit meant for PP use should work fine with either built in CT connected or artificial CT.

Long answer: There are many vintage transformers that are wound specifically with either PP or SE in mind, even SE units with CT's, that will misbehave if used in the other application. I've seen 15 dB notches at 12 kHz with some vintage PP types used SE. With an unknown you have to test. Every SE UTC with CT I've tested gives better response in PP also. It's a deep well.....
 
Hi, Kevin just sent me an email that the 6 steps for time constant are not possible to do with rotary switch
as original Fairchild uses more complex circuit for time constant.

Can we talk about this?

My limited knowledge tells me that every pot value can be copied with a fixed resistor value. Or am I wrong here?
 
[quote author="Purusha"]My limited knowledge tells me that every pot value can be copied with a fixed resistor value. Or am I wrong here?[/quote]
you are right.

we are not building a fairchild one to one clone - this would be poor.
but the poor man shares the same topology :green:

for the poor man time constant switch:
use what ever you prefer. a pot if you like unstepped control, an expensive 24 steps elma switch, or a 6 step to have a more original look alike.

but for sure the time constant steps won't be the same side by side with an original fairchild ...
 
for the poor man time constant switch:
use what ever you prefer. a pot if you like unstepped control, an expensive 24 steps elma switch, or a 6 step to have a more original look alike.

but for sure the time constant steps won't be the same side by side with an original fairchild ...
Click to expand...

OK, that is good enough for me :thumb:

Thanks!
 
[quote author="Purusha"]Hi, Kevin just sent me an email that the 6 steps for time constant are not possible to do with rotary switch
as original Fairchild uses more complex circuit for time constant.
[/quote]

you should be able to easily copy the time constant switch. you'd just have a bunch of components hanging off the switch...
:grin:

if you go looking at the 670 schematic, it's simply a 2x6 switch, that switches in various networks of R and/or C across the main "fixed" RC... just like our pot and his little friends sit across the fixed RC in the poorman.

The issue would be if the circuit driving this (ie, the sidechain amp and transformers!) can drive it the same way that the sidechain amp in the fairchild does.... and if the gain reduction circuitry in the poorman pulls the same load that it does in the fairchild.... that's what I was asking in a roundabout way earlier on.

If not, then the RC circuit will act differently, and values would all need to be scaled to suit.
 
[quote author="Purusha"]Maybe Volker can share with us how he did his time constant with 6 steps?
What resister values and so on.[/quote]
mhm, this was really hard to get right, will keep this as my secret :green:
how to substitute a 10K lin pot with a 6 position switch and 5 resistors ...
where is my calculator ? what is 10K / 5 ??? :green: :green: :green:
:oops:
 

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