Hello again, plus a couple of Q`s.

[GeirW]

Gday.

Ciao. everyone, am back to eventually learn some more.
Have been abroad for some time, (Sicily - working)
Am still haven`t got around to make my pp el84, still
collecting parts. And regarding that i have a couple of questions,

1. There was a guy that gave me a old Tanberg amp/radio.
am gonna build another, but i think am going to change
some components in this one. (i think this is from 57-58)
apparently it uses ecc83 to drive el84, what`s the equalent
of ecc83, or is it a good tube. (telefunken).

2. To everyone known to tanberg stuff.
Is it someplace on net, i can read up on the transformators
used in there models. (they don`t have any labeling.
just that it`s rosses metal/covered in "tar".
(fecking heavy)

 

[GeirW]

Gday.

Q.1. over at duncan amps, 12AX7 is mentioned as a
equalent tube. No modding needed?
How will it sound, atm. there`s one ecc83 on 2 x el84.

 

[SY]

ECC83 is just the European equivalent number for a 12AX7. Same same.

 

[GeirW]

Gday.

OK. is there some other options.?

 

[SY]

12AX7s are common, inexpensive, easy to get, and easy to apply. What else are you looking for?

 

[GeirW]

Gday.

Well. for that 75-20 in question, i think i better change
most of the caps and resistors in signal path,
since the amp. itself are quite old. I reckon they have gone
bad after 47 years. (the caps. are Hunts, not sure about the res.)

Regarding the tubes, i just is exploring the option
of replacing them. You say 12AX7 is the same as ecc83,
and i reckon the 6BQ5 is equivalent of el84?.

I am on the look out for one particular though,
It`s a big DC cap. (tread in the electrical parts)
(printed on the can.)
Red res. 40uF 350v
Max Ripple 350MA
Yellow 20uF 350v
Blue 10uF 350v

 

[SY]

Yes, 6BQ5 and EL84 are the same thing. And are also cheap, plentiful, and good quality.

You might consider doing the restoration in stages. Replace the electrolytic caps, input and output jacks, potentiometers, and any selenium rectifiers, then see how it all works. Next in line would be coupling caps, then resistors.

 

[GeirW]

Gday.

stages

yes. i have to, no matter what, it`s a mess in there.
one at a time.
btw. there isn`t used jacks, just pipes to put the banana inn.

 

[EC8010]

You definitely want to replace those "Hunts" capacitors. The bodies tended to crack and let moisture in, making them leaky. A leaky coupling capacitor could destroy a perfectly good EL84.

 

[mcs]

Yes, I have seen those Hunts in Danish radios also - they are terrible! I also have a Tandberg 64 full of them waiting to be restored...

And conc. the ECC83. If you already have a Telefunken ECC83 there, you wont be able to find a better tube - just leave it. If the EL84s are Philips, Telefunken, Valvo etc. they are great also. You can try buying some new ones, but the old ones may turn out to be better.

Best regards,

Mikkel C. Simonsen

 

[DigitalJunkie]

A leaky coupling capacitor could destroy a perfectly good EL84.

And/Or an Output or power tranny!
Watch out for red plates.

 

[GeirW]

Gday.

Yes. the 84`s are telefunk to, i have searched here in norway
for someone that have original telefunken left ,
but no luck. Does anyone of you a clue where i can obtain some,
or are they gone.?

 

[mcs]

They are very hard to get and very expensive. But if you have the old tubes, why do you want replacements? The ECC83 is fine - the TFK ECC83 tubes last nearly forever. The EL84 tubes may be worn, but not nescesarily. Try getting some Russian EL84 tubes (cheap) and compare.

Best regards,

Mikkel C. Simonsen

 

[GeirW]

Gday.

here: http://www.demostenes.no/2.0/nor.htm
they got sovtek el84 for 8$. a tube.
For not so long ago they offered matching pair svetlana
for ca. 20$.

 

[GeirW]

Gday.

Replace any selenium rectifiers, then see how it all works.

yes.. but there is a slight problem, the rectifier here, is a
siemens aleminium cased one.
pic. of the type here:
http://home.arcor.de/w.zucker/elektronik/verschiedenes/selen-gleichrichter.jpg
type:
SSF
B 250v 100C
Kc 0.6b 22/8

 

[mcs]

Just replace the rectifier with a W04G or similar standard rectifier bridge. You may need to increase the filter resistors in the powersupply to get back to the original voltages. I'll have a look at the schematic.

Best regards,

Mikkel C. Simonsen

 

[Miniwatt]

This may be a real newbie question, but why would you want to replace the -working- resistors? I was just looking at some really old radios if I could use the resistors for my amp..

 

[mcs]

why would you want to replace the -working- resistors?

Because a selenium rectifier has a higher voltage drop than a silicon rectifier. So the output voltages would be too high with the original resistors.

Best regards,

Mikkel C. Simonsen

 

[SY]

Geir, I was imprecise in my language. By "replace" I did indeed mean with modern silicon rectifiers. Whether or not you'll need to change power supply resistors depends on what the circuit looks like, but yes, that may also be necessary.

 

[GeirW]

Gday.

I have tried earlier to attach the shematic,
but the image size is to big.
Am attach it as a zip. for those who are interested.
(never mind the radio part, am going to make a replica
with only the ps/powerstage.)