Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: isaac_teller on July 03, 2024, 04:10:56 am

Title: Correct component value
Post by: isaac_teller on July 03, 2024, 04:10:56 am

Hello. In the schematic of the preamp of the Soldano SLO100 there are 2 symbols of a LED(VR1 and VR2). Usually VR stands for a potentiometer. Does anyone know if the actual component is a LED or a potentiometer? If so, what value? Thank you.
https://el34world.com/charts/Schematics/files/Soldano/Soldano_slo100.pdf (https://el34world.com/charts/Schematics/files/Soldano/Soldano_slo100.pdf)

Title: Re: Correct component value
Post by: isaac_teller on July 03, 2024, 04:41:48 am

Found the answer.
https://robrobinette.com/images/Guitar/Soldano/Annotated_Soldano_SLO-100_Schematic_with_Signal_Path.png

Title: Re: Correct component value
Post by: sluckey on July 03, 2024, 07:16:15 am

The answer is right on the schematic you posted in the original post.

Title: Re: Correct component value
Post by: Latole on July 03, 2024, 07:30:35 am

VR = Variable Resistor.
These VR in this amp are a light activate resistor

Title: Re: Correct component value
Post by: sluckey on July 03, 2024, 07:46:48 am

VR1 through VR4 are VTL5C1 opto-isolators and are used as on/off switches in this amp circuit. VR is a very poor reference designator for an opto-isolator.

Title: Re: Correct component value
Post by: Latole on July 03, 2024, 07:58:05 am

What I see ;

Title: Re: Correct component value
Post by: sluckey on July 03, 2024, 08:07:56 am

Quote from: Latole on July 03, 2024, 07:58:05 am

What I see ;

... does not apply in this case. The VTL5C1 (https://www.tubesandmore.com/sites/default/files/associated_files/r-vtl5c1_2019.pdf) contains a LED that is electrically isolated from a LDR.