• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

FREE Dynaco tube manuals

Bob01605

Bob01605

Member
Banned
For those into Dynaco tube audio > Roy Mottram on the tubes4hifi web site now has listed 15 Dynaco tube manuals that you may download for free. You can download the following Dynaco tube manuals at the link listed below.

1. Dynaco FM-1 mono tuner manual
2. Dynaco FM-3 stereo tuner manual
3. Dynaco FMX-3 multiplex manual for the FM-3
4. Dynaco Mark 2 power amplifier manual
5. Dynaco Mark 3 power amplifier manual
6. Dynaco Mark 4 power amplifier manual
7. Dynaco Mark 6 power amplifier manual
8. Dynaco PAM-1 mono preamp manual
9. Dynaco PAS-2 stereo preamp manual
10. Dynaco PAS-3X stereo preamp manual
11. Dynaco PAS-4 preamp owners manual
12. Dynaco SCA-35 integrated amplifier manual
13. Dynaco ST-35 power amplifier manual
14. Dynaco ST-70 power amplifier manual
15. Dynaco ST-70 Series II power amplifier manual

http://www.tubes4hifi.com/downloads.htm

Bob Latino
 
Register to hide this ad
I think that Roy now has on his site the most comprehensive list of FREE Dynaco tube manuals anywhere on the internet. Personally, I have never seen before the PAM-1, PAS-4, Mark VI or Mark II manuals ever posted up for FREE anywhere on the internet.

Now the question is > How are those dudes who sell reprints of these manuals on EPay for $5- $7 a copy plus shipping gonna make a buck ? LOL

Bob Latino
 
Yeh, this prompted me to get out an old FM1 that I've been curious about. It's supposed to be mono, but has two outputs. The manual solved the mystery by describing the optional stereo board.:banana: I should have it up an running in a couple hours.:music:
 
Any MK VI owners here?

The 8417 outputs can be changed to 6550/KT88 with the replacement of 2 caps and 2 resistors in the bias supply.

Changes are as follows:

R102 to 6.3k
R104 to 10k

C103 to 100uF
C104 to 100uF

I also have the pictoral drawing of the underchassis wiring for the MK VI, it won't fit my scanner, but i'd gladly shoot a hi res photo of it for anyone who needs/wants it, drop me a PM.
 
Awesome! I restored the single MkII I have a year ago, but never had the manual. Glad to see it stated by Dynaco that a slight red plate glow is normal on the EL34 tubes. I was always sort of worried about that. Thanks for posting the link!
John
 
Re: Dynaco Mark II bias voltage and cherry red plates

sloober said:
Awesome! I restored the single MkII I have a year ago, but never had the manual. Glad to see it stated by Dynaco that a slight red plate glow is normal on the EL34 tubes. I was always sort of worried about that. Thanks for posting the link!
John
Click to expand...

John,

The Mark II was Dynaco's first product and was released in 1955. They ran those tubes HOT but got away with it because they were using higher quality EL34 tubes (Mullard's and some USA made tubes) than are available today.

What they did was use a 12 ohm bias resistor and had the user bias a PAIR of EL34's at 1.56 volts DC. This works out to 130 milliamps per tube pair or 65 milliamps per tube. 65 milliamps per each EL34 tube is pretty HOT for an EL34 and it is no wonder sometimes the plates turned red on a few tubes. If you keep that 12 ohm bias resistor in there you are wise to bias at a lower level than Dynaco suggested. The conventional wisdom today with an EL34 is to bias at 40 to 50 milliamps per tube. This works out to 1 to 1.2 volts as your bias voltage instead of 1.56 volts. The other thing on the Mark II is that they ran a higher B+ voltage. Pins 3 and 4 ran at 460 volts DC B+ with the 115 AC line voltage of the 1950's. Today with 120 volts AC line voltage you may be up to 470-475 B+ on pins 3 and 4 of the output tubes. This B+ voltage is more in line with a 6550 or KT88 based amp.

It is interesting to note that in 1959 when Dynaco introduced the ST-70 they changed that 12 ohm bias resistor to a 15.6 ohm bias resistor for this EL34 based amp and still recommended the 1.56 volt DC bias voltage. This equates to 100 milliamps per EL34 tube pair or 50 milliamps per each EL34. The conventional wisdom today is about 40 milliamps per tube. This will give longer tube life and the same sound quality as 50 milliamps per tube.

If Mark II users continue to run an EL34 at 65 milliamps per tube and a high B+ voltage some will get cherry red plates and nearly all will get short tube life. The EL34's of today are not designed for 470 volts or so B+ and 65 milliamps. Any Mark II user is wise to change out the bias resistor with the 15.6 ohm bias resistor of the ST-70. You can buy a pair of new 15.6 ohm bias resistors from Dynakitparts.

Bob Latino
 
You must log in or register to reply here.
Back
Top Bottom