Hum and tube glowing red on my Foreplay ll

[hron61]

I see that cap now, i thought it was a type of resistor. Just used to seeing a standard shaped cap.
I'll reflow that one also as i only checked for a loose connection on it earlier.
I'm curious now about the sweet or sweetest whispers, since i dont have my original paperwork from when i purchased the foreplay, i'll research it further for external indentifiers of each. I'll post a seperate thread for that info.

[hron61]

The 3 power supply caps arrived today and got them installed.
Will power up tomrw and check voltages and resistance and if all goes well i'll fire it up and see if anything changes and report back. I'll order that .1uf cap that I overlooked asap too.

[hron61]

The 0.1uF capacitor is located between the right-hand volume control and the adjacent B tube socket - I apologize, I was working from the circuit diagram instead of the physical layout (too lazy to go downstairs and pull out the manual ...).

For the volume control, I was just thinking it might have a bad ground connection or  switch contact. There were two different volume control switches over the years, called "Sweet Whispers" and the later "Sweetest Whispers" - I think you have the first one?

Your voltages are only 7% low, well within normal tolerances.

I'm pretty sure i have the Sweet Whispers. I bought the fp in 2003 but i do remember the manual said rev2. All my paperwork and manuals were lost back in 2004
I found an old post that said the Sweetest Whispers were used in Foreplay lll.

Btw, would you have replacement recommendation for the 0.1 cap? I've been searching and so many choices and i just want to make sure i get a correct replacement. Much appreciated.

[Paul Joppa]

The 0.1uF cap should be rated for at least 100 volts. (The original is "400v, metal film"s. It, along with the two resistors to which it is connected, raises the filament power bias voltage to around 45-50 volts. It is NOT in the audio circuit, so nothing critical. It is unlikely to be a problem unless it is incompletely soldered, so re-soldering it probably sufficient. It and the two resistors are all crammed into the pin 9 solder lug of the B tube - it's a tight fit, which is a risk factor in making good solder joints.

[Paul Birkeland]

Btw, would you have replacement recommendation for the 0.1 cap?

Leave the one you have in place.  Those things are extremely long lived.

[hron61]

Thanks for the info on what the 0.1 cap is for.
And solid advice from both of you about it, thanks for that.

It is very tight in there and i do have continuity in the connections of it and the solder doesnt look cold, so i'll just let it be. Dont want to create an issue if its not an issue.

[hron61]

I thought i would post a quick update on the situation and to thank you for trying to help figure this out for/with me.

I havent tried hooking the system up to a grounded electrical outlet just yet, i ordered resistors to make a shorting plug for the fp outputs and waiting for those. I would like to check the hum level.

A quick history note...when first built back in 2003 with the extended version installed at the get go
it was hooked up to my WL Laurel 300b mb with Klipsch Forte's and a Thornes turntable with diy cables of belden 89259 ic and belden 89364 for the pc and the hum was barely noticeable and only and only if i put me ear within a couple of inches from the speaker BUT it was plugged into a properly grounded electrical system. Everything played very well with each other and sounded amazing, then packed away.
Fast forward to today 22 years later and just the foreplay is being used Without a grounded outlet.
Its hooked to a solid state adcom gfa5500.

I did hook it to another adcom amp i own, a ss gfa535 and got the same hum as the with the 5500 amp.
Another thing i did was used my Luxman ss R115 receiver as a pre and hooked it up the 5500 and got Zero hum, quiet as a mouse.

I installed new power supply caps in the foreplay, reflowed all ground connections, did the chop stick testing., and tried multiple tubes and hum is still there.
Im not into electronics like alot of members here but i can follow directions in laymans terms and can solder very well.

Im still waiting to bring the system to my buddy's store to hook it up to a grounded outlet, im hoping that it just needs to be grounded.
For safety sake the Foreplay and the Adcom are plugged into a GFCI ext cord while im using it.
I'll post back after the hum is measured and i hook it to ground which should be soon i hope.
In the meantime feel free to toss anything else out there, im all ears and appreciate the help.

[Paul Joppa]

This is a real puzzler!

I still suspect a ground problem, but a grounded outlet could easily be a red herring. It's not much help, but as I recall those copper ground wires were a real bear to solder - the insulation was extremely hard to get through or burn off. And terminal 14 seems to have a bunch of them, which makes it even harder. It would not surprise me if a connection failed there.

[hron61]

Yes, it sure is.

Thats funny that you mentioned terminal 14 ground.
Late last night i was thinking the same thing.
I will put great effort in totally reworking all connections on that area.
Last night i watched some soldering videos on this sight that doc(thanks doc) had posted years back and it got me thinking about a good mechanical connection before the solder is applied and proper wire stripping, how very important that combination is.
One of the videos showed just how important flux is for the metal. A very eye opening matter to say the least. Oxidation of the metal must be eliminated.
I also use the Cardas Quad Eutectic Solder and have a container of their flux that I will make sure to use on that area as well.

[Doc B.]

There is plenty of flux in the core of the Cardas solder. Don't add extra. That will make things worse.