Sound City 120

[Vucinic]

Hallo all,

I'm new on this forum. I need some help, please. Noise from V2. I changed 5 different tubes, no changes. Still sensitive on hitting the tube. Also i cant measure VDC at pin6 V2. When i touched turret after load resistor to measure i have loud bass noise.

Thanks

[Vucinic]

"experts"

OK. I came up with conclusion. Of all of the "experts" at this kind of forums, actually no one know or understand activ tone stack of Sound City MKIV and everybody avoid to speak about or called the amp Sound Shity, or rebuild the preamp to DR103 or something easier.

[nosaj]

OK. I came up with conclusion. Of all of the "experts" at this kind of forums, actually no one know or understand activ tone stack of Sound City MKIV and everybody avoid to speak about or called the amp Sound Shity, or rebuild the preamp to DR103 or something easier.

Being snotty is surely not a way to invite discussion of a circuit. Provide a schematic for your amp.

nosaj

[Helmholtz]

OK. I came up with conclusion. Of all of the "experts" at this kind of forums, actually no one know or understand activ tone stack of Sound City MKIV and everybody avoid to speak about or called the amp Sound Shity, or rebuild the preamp to DR103 or something easier.

So, that's it?

If not, start with providing a schematic.

[frus]

http://soundcitysite.com/sc_120_2.jpg

[frus]

My message got deleted, I could only screenshot it...

[Vucinic]

Sorry i dont know how to upload schematic, i try first time. It's model with 22R and 66R catode resistor on power tubes.

[Vucinic]

https://www.google.com/url?sa=t&sour...JDMWjPUOR4KC2z

[drewl]

I had one, sounded great once you learn to dial them in.

If you don't have voltage on v2 pin 6, check the plate resistor.
It could be open, or check the coupling cap.

[drewl]

[ATTACH=CONFIG]54546[/ATTACH]
My message got deleted, I could only screenshot it...

Those 1meg bandpass resistors are usually the cause of him and his from the preamp.

It's a pain but best to just replace them.

[frus]

You mean with metal film resistors?

[Vucinic]

I have voltage, but if I try to measure with MM i have huge loud hum. And every tube i put there is sensitive on touch. I change the resistor and the coupling cap. When i measuring before the resistor, i have 274 VDC and little hum when i touch with MM. After resistor is.....

[Vucinic]

Ok, i will change them. Thanks

[Vucinic]

It's was a grounding of a filter caps. Preamp filter caps sheared same grounding point with PS filter cups. Thats not all of the hum but the most. I'm going to keep looking.