Dynacord Eminent I

[SIMPLINHO]

Hi all.

This is my first post, and I need the voltages chart of
the phase inverter, or a copy of the schematic ( not
the one on the net, it´s not good enought ).

Thank´s.

Simplinho

[vintagekiki]

Hi S.
http://www.peel.dk/Dynacord/Dynacord_Eminent.pdf
http://www.peel.dk/Dynacord/Dynacord_Eminent_1.pdf
http://www.peel.dk/Dynacord/Dynacord_Eminent_1_T.pdf

[SIMPLINHO]

Hi vintagekiki.

Thanks for your help, unfortunately this are the dirty ones,
they are not very legible, some values can´t be read.
As I said, I need the voltages chart of the phase inverter,
to check my amplifier, because after convert it in a power
amp ( phase inverter + power stage ), distortion have
increase, and power have decrease.
Once again, thank you very much.

Simplinho.

[Gtr_tech]

First print looks fine to me. I'd start by replacing the pwr supply caps then start digging deeper.

[Albert Kreuzer]

First print looks fine to me. I'd start by replacing the pwr supply caps then start digging deeper.

The first print isn't the Eminent I.
The second one is.

SIMPLINHO: What exactly did you change? Can you undo the change and see if everything is normal again?

Replacing the electrolytics is a good idea - after you have found the problem.

Cheers,
Albert

[SIMPLINHO]

Hi all.

SIMPLINHO: What exactly did you change?

Dear Albert Kreuzer, I´ve follow the second one schematic,
I did a reverse engineering to confirm the values of the
resistances, small caps and diodes.
I´ve change:
Power supply
-BY 127 - 1N4007
-B+1(CT) cap 50uF/450v,B+2(after choke) cap 50uF/450v,
B+3(phase splitter ECC81) 47uF/450v with a 1K/2W.
-Board 85002, not used.
-Board 88001
-E75C40 - 1N4007
Board 88002
-820 ohms 3W
NFB on the 4 ohms tap.

All things are new, except PT, OT, Choke, and trimmers.
I must say that on the EL34 tube´s the voltages are right.
On the ECC81 with B+(3) = 415V I have:
-1 - 80V
-2 - 0V (??)
-3 - 3V
-6 - 285V
-7 - 0V (??)
-8 - 130V

I only use the phase inverter and power stage, i think
there´s no problem on it, right ?

Simplinho.

PS: Sorry for the posting on the wrong place.

[Albert Kreuzer]

OK, let's see what we have here:

Board 88002 goes to the preamp heaters. Did you substitute the choke with a 820R/3W resistor? Are there any tube heaters connected to this supply?

NFB should be on the 16 Ohms tap, but I don't think this is the problem.

ECC81 voltages:
Pin 1 - 80V seems low. What is the value of the plate resistor?
Pin 2 - 0V OK
Pin 3 - 3V within range I think
Pin 6 & pin 8 are OK
Pin 7 may be difficult to measure w/r to ground - try measuring between pins 7 and 8.

What is between your input jack and pin 2?
Can you lift the capacitor between pins 1 and 7 and inject a signal (through a cap) into pin 7? You'll need a fairly big signal, but does it come through undistorted?

HTH
Albert

[SIMPLINHO]

Hi.

The board for preamp heaters is the 85002, not the
88002, and it´s not in use.
I didn´t substitute the choke with a 820R/3W resistor,
I switched the 2W with a 3W.
Between the input jack and pin 2, there is the 0.033uF
and the 100K resistor. On the jack I put a 1M resistor
to ground.
I have another problem, on the pin 7 now I can read
60V, I think the tube is dead. I´ll buy a new one.
Thanks for your help.

Simplinho

[Albert Kreuzer]

Hi,

the 60V reading at pin 7 is not necessarily bad. The resistance of your meter plays a role here. Measure the voltage from pin 8 to ground, then measure from pin 7 to pin 8.

Do you have a DC path from pin 2 to ground? There has to be a resistor (~ 1M) AFTER the 0.033 cap to ground.

Check this before you buy a new tube.

Cheers,
Albert

PS: Found the resistor on board 88002. Yes, 3W is a good idea.

[SIMPLINHO]

Hi.

At this moment I am in my job, but when I am at home,
I will do the measures.
I will exchange also the resistor of 1M, and see what it
happens.

Edit:
I already did the new measurements, and I found the next values:
-Pin 8 to ground = 131v
-Pin 7 to 8 = 4,6v
I keep on having the same problems. Perhaps it is better to try
with a new tube.

Simplinho

PS. I have your site in my favorites, from 2005, and am
intending to build the bass preamp - tube sound with
JFET technology, to use with this poweramp.
But I never intended one day to be exchanging messages with you.
Principal reason, my English is the worst.
I have been using a translator on-line, to
help me. Thank goodness that they exist.
The world is even small!

Cheers.

[SIMPLINHO]

Hi.

Today I will do a test with a ECC83. A friend lent me one.
The results may be slightly different but there should be
no problems. I hope this time everything runs smoothly.
See you soon.

Simplinho.

[Albert Kreuzer]

Hi Simplinho,

not quite sure if I read this right:

Between the input jack and pin 2, there is the 0.033uF
and the 100K resistor. On the jack I put a 1M resistor
to ground.

There MUST be a resistor from pin 2 directly to ground. Else the tube will not work properly.
An ECC83 will work for test purposes, but is not ideal in this amp.

PS. I have your site in my favorites, from 2005, and am
intending to build the bass preamp - tube sound with
JFET technology, to use with this poweramp.
But I never intended one day to be exchanging messages with you.
Principal reason, my English is the worst.
I have been using a translator on-line, to
help me. Thank goodness that they exist.
The world is even small!

Cheers,
Albert

PS: Which translator do you use? Seems not so bad.

[SIMPLINHO]

Hi Albert.

There MUST be a resistor from pin 2 directly to ground.

As you can see from the schematic, there is a 680K resistor there.
With the ECC83 there is no distortion, but still haven´t +/-30W
of power. A 5W amplifier plays higher.
I am thinking of changing this phase inverter, by the "long-tail pair.
Does I can get more power?
I even started wondering if the OT is damaged. But if that is the case,
the values in the power tubes would be wrong, right?
Any help is welcome.

Simplinho.

PS:

PS: Which translator do you use? Seems not so bad.

Google is your friend, or should I say Google "ist dein Freund"
Cheers.

[Albert Kreuzer]

Hi Simplinho,

so the 680k resistor is there, good. I wasn't sure because you changed the input.
The preceding stage in the original circuit may have had more output than standard line level, so maybe you need one more gain stage before the ECC81.
A LTP a la Fender gives you more voltage swing, could be worth a try. To get the most gain out of the PI, you could take an ECC83 with the typical Fender blackface resistor values (82k/100k plate).

The OT is probably OK. Measure DC resistance across the two primary windings - should be roughly the same (+/- 10%).

Cheers,
Albert

[SIMPLINHO]

Hi Albert.

As I have an ECC83, I decided to order the rest of the parts, resistors, capacitors, etc., to build the LTP.
I hope it arrives tomorrow, so I can finish it this weekend.
I'll also check the OT to see if there is any problem.
I hope this time everything is gonna be working as it should be.
Again, thank you for your help.

Cheers,
SIMPLINHO