EV4417 6CM5 (6x) P-P Amp Schematic

[real]

Hi,

I have recently acquired 4 EV4417 amplifiers which I think are Philips brand. They were rack mount amplifiers from a cinema that were removed (still working) 10 years ago.

They have a mu-metal mounted transformer on the input, a 12AX7 driver tube and 6 6CM5 (aka EL36) pentodes in push pull for the output. I am pretty sure these amplifiers were built in Australia.

I have tried searching here and with google, but with no luck. Does anyone know anything about these amplifiers or ideally have a schematic? Specifically, I want to know if their output is a 70/100V output or a 4/8 ohm output.

Thanks for any help anyone can offer,

Chris.

[mississippi]

Look here. The amplifier is at the bottom of the page.

[real]

Hi Mississippi,

Thanks so much for that, it is a real help!

Chris.

[mississippi]

Your welcome.
regards.
M

[gingertube]

Chris,
A search found this thread.
I picked up a similar Philips amp, 2 x 12AX7 + 6 X 6CM5 (EL36) last week.
The link above gives "access forbidden" message.
Do you have the schematic in electronic form which you could email to me?
I've done a circuit trace but the amp, which I'm fairly sure was intended for PA use, has been modified for use as a guitar amp, so original schematic would be valuable.
I'm not sure of the power output from this thing and am not game to turn it on to check voltages untill some suspect looking electrolytics and the OA210 rectifier diodes have been replaced.
Cheers,
Ian

[real]

Hi Ian,

Here is the schematic. It is ok, but doesn't have voltages for the valves, only the rail voltages.

Do you know anything else about this amp? I was told that the ones I got were from a cinema - so I'm not sure if they're for 4/8 ohm loads or 70/100V loads and I have not even tried connecting them up (I wouldn't anyway because of the suspect capacitors, as you have also noticed).

If you know anything about the amp (other than info from the schematic), then let me know.....

Cheers,

Chris.

PS You can't be emailed directly, you have it disabled

[mississippi]

The amplifier has a low ohmic output winding and a 100V output winding.
You only have to connect the right wires.
The amplifier on the photo's is connected for low ohmic speakers.

@ gingertube:
there must be a settings problem with your browser because almost everybody can reach the site without any problems.

Here is the link again.
http://members.chello.nl/m.janssen36...ith-valves.htm

[mach1]

I believe Graham Dicker

GTD@bettanet.net.au

Has worked on a few of these. Very affable fellow if you drop him a line.

[gingertube]

Chris,
Thats the amp exactly. Mine has another 12AX7 and a microphone coupling transformer on the front with some tone and volume controls. There is also a trick limiter circuit.

The Output transformer has 25 V, 50V and 100V taps

Making a few assumptions and using a possibly dodgy method:
From 6CM5 Data Sheets, power output is 120 Watts, Raa of Output Tranny is 1200 Ohms
That means output transformer primary voltage swing of 380V

The 25 Volt Tap would then be (25/380)^2 x 1200 = 5.2 Ohms - so OK for 4 Ohm or 8 Ohm speaker box.

The 50V Tap would then be (50/380)^2 x 1200 = 10.8 Ohms - so Ok for 8 or 16 Ohm speaker box.

Similarly the 100V line give 83 Ohms - Not much use without a 100V line matching transformer.

My amp originally had the 50V line wired to the speaker binding posts on the back panel.

Cheers,
Ian

[gingertube]

Check out the power supply on the schematic. I had to look twice until I worked out whar was going on.
Clever way to generate a 1/2 B+ supply for the screen withiut needing an extra rectifier.
Cheers,
Ian.