Opus 6 HiFi-System Licensed by Armstrong

I'm working on re-capping a Telefunken Opus 6 and I came across a Pyramid brand capacitor that isn't listed in the parts list.   It appears to be a big electrolyitc capacitor 16uF - 450V that's mounted on top of the chassis by the transformer. Here's a picture the capacitor in question.

Does anyone know if this was the correct capacitor installed by the factory? I was wondering if someone may have replaced the original capacitor with the wrong size since I couldn't find this one in the parts list.  Thanks!

Anexos

• Opus 6 - Pyramid cap (226 KB)

Hello Jamie,

I have never saw one elko cap like this inside a German radio. It is not one original replacement for sure.

Cordially, Bruno.

Thanks for the reply Bruno!  Do you know if the 16uF - 450V is the right value capacitor for this location? The radio works now, but the sound starts to fade after about 10 minuites and the radio warms up. 

Sincerely,

Jamie

You are wellcome Jamie, 

I do not have that radio. On the model's page you have all the technical information: the circuit, the parts list and the 3-D diagram to identify the capacitor over the output transformer. Then you can make the appropriate replacement.

Respectfully, Bruno.

The diagram shows C82, which correspondes to a 2200pF cap on the parts list. The aftermarket 16uF Pyramid cap is installed in this position. The Pyramid cap looks old too, so it's probably been in there a while.  Whoever installed this aftermarket cap wasn't even close in choosing the correct size! 

Thank you!

Jamie

Hello 

I think this cap is not original too.

Photos are not clear, but may be this "Pyramid" cap are put in parallel with C5? . C5 is located below on your photo, 50uF. This could be done by somebody to somewhat "improving" the sound. C5 is in series with the tweeters.

And I think that C82 are in your photo too, just between the 50uF and the piramid.

 May be, you could tell us where this cap is conected. (vg: positive to ping xxx of xxx, ...)

Regards

Please follow the radio's schematic, for capacitor replacement.

The most important thing in this radio , is to replace the selenium rectifier, with a silicon bridge rectifier and a dropping resistor.  Something that has been very well explained on this forum already, on other threads.

Make sure to replace all paper capacitors and electrlytic capacitors, and then seeing if any resistors are questionable.

Best

Just wanted to provide everyone an update on the Opus 6. I ended up replacing all the electrolytic and paper caps. The radio sounds beautiful now and I see why so many people are impressed by the way they sound.

An interesting observation I had, was someone installed that Pyramid capacitor that wasn't even listed in the schematic or parts manual, so I removed it from the circuit.  Also, before I had finished replacing all the underside caps around the EL84 tubes, the radio would sound great for about 10 minutes, then start to sound "farty", the bass would become punchy sounding.  During this time, I noticed the rear-most EL84 tube would run much hotter than the front-most EL84 tube.  Well, replacing all the caps connected to these tubes on the underside resolved that issue.  Here's pics of the new caps installed and the stand I made to hold the chassis upside down.

Anexos

• opus6 under_new caps (242 KB)
• opus6 stand2 (203 KB)

Please check the selenium rectifier, if it is running VERY hot, and check to see what voltage it is kicking out in DC.  These rectifiers are known to be bad, and a bad one, can damage your transformer!

You are searching for some one with experience in improving the receiving ability of this set.    Maybe some one posting here his results.

I to not have this radio, I only can say to you, in this early time 1955/56,  the ferrit -antennas have mostly  40 to 60% from sensitivity of designs from now.
In this time, the sensitivity of the extern Antennas has priority! 

I do not now,, if you mean your set has an failure, or you want to redesign the circuit. From where is your indention of:  Radio is receiving maybe 65-75% of its potential.
Have you make any measurements about sensitivity an grid 1 ( pin2) ECH81 on IF and RF?
First:
The ratio sensitivity on IF to RF on 1Mcs should be: 1 to 1,2 to 1,3 ( for example: 10 uV on IF  to 12 uV on 1Mcs) This is very important for the ratio of signal to noise!
Second:
Additional,  from antenna to this G1 ECH81 the RF is the only value to improve  the reception.

The IF gain makes only more noise and wanted power on the speakers. The volume potentiometer can compensate this over a with range! 

Have you test the value of local-oscillator ( Volts AC or Volts DC) on g1 of Triode ECH81?
To you have a Signalgenerator?

O.K. I am waiting for your comments,
Regards Hans M. Knoll