Can't get much help on other forums

[Paul Birkeland]

Please measure across the cap, not using the chassis as a reference.

-PB

[rockpassion]

Will do.

Richard

[rockpassion]

Paul,

To make sure when you say across the capacitor  I am assumiung you mean to put my black probe on one side of the capacitor and the red probe on the other. 

If so I got the following readings.  C8 - 487.8 VDC, C9 - 585.4 VDC and C10 -584.8 VDC. 

Richard

[Paul Birkeland]

OK, that is more like it.

The chassis of your amplifier isn't grounded, this is a problem.

I'm guessing you don't have a 3-wire power cord on the amp?

This is a safety issue to address immediately.

-PB

[rockpassion]

Paul,

You are right.  It is an old two prong.  Where would I attach the ground wire in the amp for a three prong power cord.   

When I look at my old BH Seduction the IEC connectors ground terminal goes to the chassis and also to the transformer.  So would I run a wire from both the chassis and the transformer.  If so, I think I know how to ground the chassis, but looking at the transformer I do not know what point to use as ground. 

But I do have a question.  If a capacitor is supposed to block DC voltage why am I getting readings showing DC voltage. 

Richard

[Paul Birkeland]

You are right.  It is an old two prong.  Where would I attach the ground wire in the amp for a three prong power cord.   

When I look at my old BH Seduction the IEC connectors ground terminal goes to the chassis and also to the transformer.  So would I run a wire from both the chassis and the transformer.  If so, I think I know how to ground the chassis, but looking at the transformer I do not know what point to use as ground. 

Yeah, the Seduction is a good model to follow.  You probably have 2 prongs coming in, and one of the prong is soldered to the chassis (bad).  You want to add a 3 prong cord.  Hot and neutral go to the power transformer primary (through switch/fuse, add a fuse if there isn't one), the earth connection goes to the chassis at the closest possible place from where it enters the amp.

But I do have a question.  If a capacitor is supposed to block DC voltage why am I getting readings showing DC voltage. 

Capacitors store charge (good for a power supply), and offer a reactive impedance to AC (also good for a power supply, power supply noise is shunted through the cap to ground).

The DC blocking application works for coupling capacitors, where the cap offers relatively low AC impedance while blocking DC voltage from the next stage. 

-PB

[rockpassion]

Paul,

Thanks!!!  I checked the schematic and traced the 115 VAC wires  to both the on/off switch and the fuse directly, one wire to each.  By what you are saying I am going to find a point close to where the ground wire from the 3 prong cord originates into the chassis and connect it directly to the chassis. 

I might not do that today but as soon as I do should I measure the same capacitors in the same way again? 

By the way,  I think I have learned more in the last 30 days than in the previous 5 years of just constructing the kits.  This is great.  I love this forum!!!

Richard

[Paul Birkeland]

Yeah, you really want to nail down the whole power cord thing before doing anything else, I should've brought it up earlier.

You should find that one of the wires from the 2-prong cord connects to the chassis somewhere.  It's also possible that they just come in and go to the primary, and that the chassis is floating (gasp!).

Once you have the power cord properly installed, then you can try measuring that cap voltage again.  If you get something funky, you will want to connect power supply ground to the chassis as well.  (I like doing this close to the RCA jacks or where the signal comes in to the first tube)

-PB

[rockpassion]

Paul,

These amps do not have a power cord.  There are two wires that come from the power switch and one from the fuse.  I attached a three prong cord with the ground attached to a screw on the chassis. 

I rechecked the voltage on the three Solen capacitors and found the voltages very close to the previous readings.  There were as follows.  C8 First reading 487.5 VDC second 486.3 VDC, C9 first reading 585.4 VDC second reading 583.6 VDC, C10 first reading 584.8 VDC second reading 583.3 VDC.

Another interesting thing is, there is a meter on the front that measures  the two 807's and the OD3/VR150's and shows whether they are good or bad.  It registers for the first 807 that it is good  but the second 807 and the OD3/VR150's does not even register.  I have a few 807's and will try them along with another pair of OD3/VR150's.

I Look forward  to your response.

Richard

[Paul Birkeland]

OK, it's good that the chassis is grounded.  I would recommend also grounding the power supply to the chassis.  This is often best done up where the RCA input jacks are. 

-PB

[rockpassion]

Paul,

I looked at my Seduction and see the transformer in it is grounded back to the ground connection on the IEC connector.  Unless you tell me otherwise, I will run a wire from a screw connection where the transformer is anchored to the chassis and then directly to the ground wire on the three wire power cord.   Does the transformer itself ground the external metal case surrounding the transformer?  I assume it must.  Looking at the schematic I also see the Center Tap is grounded to the bridge connection between C9 and C10, but I assume this is a System Ground and not grounded to the chassis.

There are no external connections on the amps.  I only have exposed wires.  If I can get these ampos up and running I will install all the connecting devices I need directly to the chassis.

Regards

Richard

[rockpassion]

Paul,

I grounded the Transformer to the ground wire on my power line.  I did notice a slight decrease in the volume of the hum.  I also remeasured the C8, C9, and C10 capacitor.  I noticed a slight increase in DC voltage to C8 from 487 to 493, C9 from 585 to 591, and C10 from 585 to 591. 

Any thoughts on what to do next.

Thanks

Richard

[Paul Birkeland]

Measure AC millivolts across the speaker taps and let us know what you see.  It would be a good idea to short the inputs while doing this measurement.

-PB

[rockpassion]

Paul,

Are you saying the taps on the Output transformer?  In this case the C and 8 ohm tap.

Richard

[rockpassion]

Paul,

Just to make sure on the input side, I have the two input wires twisted together and shorted to the chassis.  Should I instead use a shorting RCA plug. 

I took the measurement across the O and 8 ohm tap on the output transformer.  I tried using millivolts AC on my Voltmeter but got an OL reading.  So I switched to Volts AC and got 4.78 VAC. 

Richard