Need help identifying old diode in WSW preamp

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

Admiral-dk

Member
Joined
Apr 1, 2022
Messages
12
Location
DK
My absolute first thought when I looked at the Picture - This is a Ceramic Capacitor - but Jakob's suggestion is another posibility ....
That said - I'm sure I haven't seen a good number of the posible Diode housings from back then .... but all the Germanium ones I have seen where in Glashouses .... (painted or not).
 

David_H

Active member
Joined
May 21, 2021
Messages
34
Location
Austria
Sadly no - I know where to get it from but the source wants 30€ for schematics + pinout, and seeing that they are selling them they'd probably not be happy with me sharing it publicly. But since there don't seem to be any public sources available I'll probably bite the bullet and buy the schems and ask the source if they are ok with me Pm'ing it to people. Technically I could probably go ahead and do whatever with them once I bought them, but he's a very specialised guy who does great work, so I want to be respectful about it.
 

rjb5191

Well-known member
Joined
Oct 26, 2017
Messages
162
Location
Montana, USA
..this is not a line amp /preamp - it's a summing amplifier..

In another mix-amplifier from the 811-series (attached 811-514), diodes are all PSU zeners, protection, and relay decoupling. All non-critical..

Are you sure you're not looking at a NTC? Those are weird and mission-critical

/Jakob E.
Thank you. I believe you are correct that it was originally a summing amplifier; I'm now using it as mic preamp or line amp. I have no idea if it is a thermistor or not but I could see where the strange, thin leads on them could lead to that. Do you have a test for determining if it is an NTC or not?
 

mad.ax

Well-known member
Joined
Jul 22, 2007
Messages
717
Location
france
Plug an Ohm-meter accross it. Should read the same value regardless of polarity. Then use an heatgun or the proximity of your soldering iron tip to elevate the temperature. If the resistance decrease significantly, you have an NTC....
 

rjb5191

Well-known member
Joined
Oct 26, 2017
Messages
162
Location
Montana, USA
Thanks you. They only read resistance in one direction. So, I put them on my LCR meter and they appear to be a polarized capacitor around 10 uf. These appear to be quite small to be an electrolytic or that vintage. So, could they be tantalum?
 

Chandra

Member
Joined
Aug 15, 2022
Messages
7
Location
SIngapore
It seems to be a RCA type diode in TO1 case. Refer the data sheet attached.
Could be one these. Regards.
 

Attachments

  • 1N3754_RCA.pdf
    86.4 KB · Views: 0

Chandra

Member
Joined
Aug 15, 2022
Messages
7
Location
SIngapore
My apologies.
The part looks kike a polystyrene capacitor. Note how the leads are coming out from the capacitor. Typical of such capacitor, one at the center and other at the external foil to indicate which is the ground (external foil) side.
Regards.
 

AnalogPackrat

Well-known member
Joined
Apr 12, 2005
Messages
1,871
Location
Far Away From Newsom
My apologies.
The part looks kike a polystyrene capacitor. Note how the leads are coming out from the capacitor. Typical of such capacitor, one at the center and other at the external foil to indicate which is the ground (external foil) side.
Regards.
Yes, and they always have very thin leads to reduce heat flow into the device when soldering as polystyrene is easy to melt. I'd recommend placing an alligator clip on the leads to sink some heat when you desolder. Be quick with the iron.
 

PentaTech

New member
Joined
Mar 25, 2017
Messages
1
I suspect I have a bad diode in my old WSW 811 432 Line amp / preamp. When i move it physically in the slightest, it seems to go open. I would like to replace it but have no idea what it is. I can't find schematics and I can't find anything in a google search that looks similar. Its from a 1960 vintage console so I'm guessing it's germanium.

In the picture its the small brown component with fine leads and a black and green dots, down and left of center in the photo. Any help is much appreciated!
I've never seen one like yours but if it is a simple germanium diode, try a 1N60A available at Digikey. More likely, it's a 1/2 Watt Zener diode. Find the value by measuring the voltage drop across it when it's working. I'd guess the cathode is up in the picture.
 

rjb5191

Well-known member
Joined
Oct 26, 2017
Messages
162
Location
Montana, USA
Thank you. It also sounds like it could be a capacitor. I got pulled off this project but I'm going to push it up in priority and will report back. I have an LCR and a newly acquired Atlas DCA75. So hopefully between those 2 I get to the bottom of it.
 

rjb5191

Well-known member
Joined
Oct 26, 2017
Messages
162
Location
Montana, USA
After removing them and measuring them on my LCR and Atlas DCA the answer that I have that makes the most sense is that they are 10 uf polar capacitors. They all measured fairly close to each other. ESR on average at 1 khz is about 2 ohm. The only type of capacitor that I'm aware of that could have that value in that size of a package from that period would be a tantalum capacitor. Of course, I've never seen a tantalum capacitor that looked like that before. Has anyone ever seen a tantalum capacitor that looked like this? To wrap this back around, I don't believe it is one of these parts that is causing my issue.
 
Top