AVA mod Dynaco Pat-4 WOW

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E

EV-MAN

Member
Joined 2006
Built a Dyna Pat-4 kit back in the Mid 70's used it for 10 to 15yrs. Put it with the rest of the junk sorta forgot about it. It was just a OK little preamp. Went to a friends house that has a system that he put together. Walked out his house with the fever. So here I am again. Went to surfing the web looking at the new stuff & Vintage. Ran across Van- Alstine got to reading on his web site found out that he had done some mods back in the 80's for the Pat-4. Replaced the caps on the boards. Built the new power supply which is much more powerful & did the other things he recomended. And now the good part. This little preamp that was OK is now FANTASTIC. you would have to pay several hundred dollars to get one as sweet as this. Forgot how much fun it could be especially when things work....Well its off to the next project. HAPPY SOLDERING
 
juliovideo

juliovideo

Member
Joined 2009
I bought one from ebay and I did some modifications, though I do not know a lot of electronic .


Manual - http://www.tubes4hifi.com/PAT- 4.pdf


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Parts .

Capacitors
SoZo Mustard Caps
Polypropylene Capacitors

Knobs
Amplifier Knobs and Control

Cable
20 Ga. Silver Plated Teflon Wire
18 Ga. Silver Plated Teflon Wire

Potentiometers.
Potentiometers

POWER SUPPLY
DYNACO PAT-4 POWER SUPPLY UPGRADE KIT AS REQUESTED !! - eBay (item 370342575359 end time Mar-30-10 15:45:52 PDT)

ELECTROLYTIC CAPACITOR
DYNACO PAT-4 AXIAL ELECTROLYTIC CAPACITOR KIT NEW!! - eBay (item 370343722476 end time Apr-01-10 18:51:18 PDT)


Transistor
DYNACO HAFLER PAT-4 PAT-5 DH-101 DH-110 REPAIR KITS!! - eBay (item 280482953371 end time Apr-21-10 19:29:13 PDT)



Potentiometers for Dynaco Pat-4

Volumen 250k Dual Audio Taper Pot
Balance 250 K Dual Linear Taper Pot
Bass 50k Dual Linear Taper Pot
Treble 1M Dual Audio Taper Pot


Somewhat important: the original control volume.... the Loudness is a special pot that has a volume control, in this case what is done in the absence of such control is to connect the loudness to the log Stereo in the volume control,.... works perfect.


:)


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juliovideo

juliovideo

Member
Joined 2009
chopchip said:
hi,

im going through the parts list in the original manual and where the capacitors are listed not all the voltages are indicated. do the voltages indicated refer to all caps further down the list? i assume so, but am i right?

thanks
Click to expand...


You do not worry about it, buy the proper value of the components in the links I put up,.......

http://www.tubes4hifi.com/PAT- 4.pdf

.......... if you pass the mouse over and you click you going to the web.

sorry for my english :)


Cable
20 Ga. Silver Plated Teflon Wire - http://tubedepot.com/tw-20-str.html 20 Ga it's for all cable going to board

18 Ga. Silver Plated Teflon Wire - http://tubedepot.com/tw-18-str.html 18 Ga it's for all cable going to power supply and output audio



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C

chopchip

Member
Joined 2010
this is going to take a long time for me to figure out which is what.

could you please kindly list them so i and others can make reference.

i know this is probably time consuming but if you could please list them with their voltage ratings and if they are the mustard ones or the polyprops or the electrolytics.

for example the .015mfd caps come in 600 and 400 volts. which ones are the correct ones?
thanks
 
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juliovideo

juliovideo

Member
Joined 2009
chopchip said:
this is going to take a long time for me to figure out which is what.

could you please kindly list them so i and others can make reference.

i know this is probably time consuming but if you could please list them with their voltage ratings and if they are the mustard ones or the polyprops or the electrolytics.

for example the .015mfd caps come in 600 and 400 volts. which ones are the correct ones?
thanks
Click to expand...

I chose this .015 microfarads (μF)

Orange Drop 715 Series .015µF / 600V

because it is the only one that has tube depot .015 uF Polypropylene Capacitor.

I think the voltage is not important, but here the technicians of this forum maybe give you a better answer on this.

What I do know that it must maintain the polarity of electrolytic capacitors, and to put of correct position.



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C

chopchip

Member
Joined 2010
juliovideo said:
I chose this .015 microfarads (μF)

Orange Drop 715 Series .015µF / 600V

because it is the only one that has tube depot .015 uF Polypropylene Capacitor.

I think the voltage is not important, but here the technicians of this forum maybe give you a better answer on this.

What I do know that it must maintain the polarity of electrolytic capacitors, and to put of correct position.



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Click to expand...

i think voltage does matter, i understand that a capacitor will explode if it recieves more voltage than it is rated for.

thanks for you time though.

so how does your amp sound?

thanks
 
juliovideo

juliovideo

Member
Joined 2009
chopchip said:
i think voltage does matter, i understand that a capacitor will explode if it recieves more voltage than it is rated for.

thanks for you time though.

so how does your amp sound?

thanks
Click to expand...


You need proper burn-in time for a week and the sound is nice.Tighten the ground strong (1/4 plug in/out and power supply) with Lock washers internal tooth........because then you would find noise problems.

Replace if possible all RCA connectors or clean with Water Sandpaper.................because then you would find noise problems too.

Use 4% Silver Solder.

:)



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C

chopchip

Member
Joined 2010
study

i have been pouring over your pictures and have now half a list of the caps and put them in a shopping cart at that website. i got the caps from your board. now the remaining caps go on the filter pots and on the input jack i assume.

im still waiting for the patient to arrive. when it comes things will become more clear.

now i have to figure out which pots to buy.
thanks for all the help. your amp looks nice and clean, i like the knobs you put on it. i think im going to do exactly what you did.

is this the volume pot you have? Alpha 24MM Dual Audio Taper Pot 8MM Bushing

is this the balance pot you have? Alpha 24MM Dual Linear Taper Pot 8MM Bushing

i think im going to bypass the bass and treble functions as per the Frank van Alstine upgrade. how do you find those circuits to function?

thanks
 
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juliovideo

juliovideo

Member
Joined 2009
chopchip said:
is this the volume pot you have? Alpha 24MM Dual Audio Taper Pot 8MM Bushing

is this the balance pot you have? Alpha 24MM Dual Linear Taper Pot 8MM Bushing

i think im going to bypass the bass and treble functions as per the Frank van Alstine upgrade. how do you find those circuits to function?

thanks
Click to expand...

The important thing is that volume control is of 250k like the balance too ,but originally the volume control is 250k and 220k for the balance.

Volumen 250k Dual Audio Taper Pot
Balance 250 K Dual Linear Taper Pot

If you change the value of K, the sound will be different.



================

Potentiometer: A variable resistor with three terminals, a resistor and an actuator (the adjustment shaft or dial) that is used to tune a circuit by changing the resistance and potential when the actuator is adjusted. For example, volume controls are usually potentiometers. Also called a Pot. There are several types of potentiometer, described by function, actuator type, resistance material, configuration and type, as shown below.

Function

Antilog (Taper), Audio (Taper), Linear (Taper), Trimmer



Potentiometer, Antilog (Taper)

Electronics: A potentiometer in which the increase in resistance is logarithmically proportional to the rotational change, with resistance increasing slower than the rotational change. Originally, antilog potentiometers were used in balance controls that had a log/antilog dual section potentiometer (or dual gang potentiometer); however, they are rarely used in modern electronics. Also called a Reverse Audio Taper Potentiometer.


Potentiometer, Audio (Taper)

Electronics: A potentiometer in which the increase in resistance is logarithmically proportional to the rotational change, with resistance increasing faster than the rotational change.


Potentiometer, Linear (Taper)

Electronics: A potentiometer in which the increase in resistance is directly proportional to the rotational change.


Potentiometer, Trimmer

Electronics: A potentiometer that is designed to be set and then left alone for normal operation. It is commonly used for calibrating instruments, and other areas where it is necessary to tune a circuit to provide an exact gain, output voltage, or current. Trimmer potentiometers (or trimpots) do not have a shaft and must be adjusted using a screwdriver or other tool.




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C

chopchip

Member
Joined 2010
thanks for the informative reply

so now you find that the tone controls are operating well? thanks for that info, i guess i will rig up the 250k pots on both the volume and tone then.

but are those pots i posted the ones you used, i cant see anywhere in the listing on the website if they are 250k. maybe i will go back and look more closely

i checked and those are 10 ohm.

can you tell me where you purchased those pots pls? you indicate you got them from tube supply but i dont see them anywhere

thanks
 
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C

chopchip

Member
Joined 2010
Somewhat important: the original control volume.... the Loudness is a special pot that has a volume control, in this case what is done in the absence of such control is to connect the loudness to the log Stereo in the volume control,.... works perfect. QUOTE

im trying to understand what you are saying here. do you mean "Loudness" as a bass boost? that there is a pot for a loudness control which is connected to the volume pot?

im very new to this and "somewhat important" sounds critical to me and im afraid i dont understand what you are saying.
could you pls clarify a bit further?

thanks
 
M

multisync

Member
Joined 2008
I don't have a PAT 4 or a schematic, for what its worth don't worry too much about the voltage for the capacitors. Why, well the Pat 4 it look like a solid state preamp, no tubes were shown , so a good guess would be to see what the power supply voltage is and use caps at that value or higher, ex if the power supply is +30 volts then caps of 35v or higher would be fine. If the power supply is +/- 15 volts then 35volt caps would be fine as no voltage in the preamp would be higher that 15 + 15 = 30 volts. The only thing you would have to worry about is if someone connected to an input or an output on the Pat 4 to a tube device and those capacitors in the tube device were shorted and then you may I say may have to worry about a possible voltage greater in value than what you have on the ratings of the input and output capacitors in the Pat4 preamp.
 
juliovideo

juliovideo

Member
Joined 2009
chopchip said:
Somewhat important: the original control volume.... the Loudness is a special pot that has a volume control, in this case what is done in the absence of such control is to connect the loudness to the log Stereo in the volume control,.... works perfect. QUOTE

im trying to understand what you are saying here. do you mean "Loudness" as a bass boost? that there is a pot for a loudness control which is connected to the volume pot?

im very new to this and "somewhat important" sounds critical to me and im afraid i dont understand what you are saying.
could you pls clarify a bit further?

thanks
Click to expand...


Sorry for my english :)


An externally hosted image should be here but it was not working when we last tested it.



.........connecting the loudness wire together with the stereo wire in the volume control.


enjoy !!!



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