Extended Foreplay III with MJE350 Transistor Regulator Board dropping channels

[jlharden]

Extended Foreplay III has been running flawlessly for 8 or 9 years until this morning. The right side output had stopped. Swapped in another set of tubes to no avail. Checking the boards, the reg board was not lit on the A side, D1 diode, with all diodes also out on the right channel C4S board. The channel outage later flip-flopped. I prodded around(managing to blow a 270 ohm resistor in the power supply, new parts on order. Oops!.....) Anyway, it's an early regulator board with the MJE350 transistors. Mains voltage here runs 122-124v on average. I've read that voltage over 120v can cause problems with the older boards. Should I try to install new transistors or a newly populated board? Are the parts still available? Also, I'm not against getting this in the hands of a good tech for a full tune-up. Any recommendations? I'm a journeyman carpenter with many years under my belt. I've learned the values of a specified skill set and not afraid to put this in the hands of someone with superior knowledge of the design. Thanks in advance.

Jerrod

[Paul Birkeland]

Hello Jerrod,

You are more than welcome to send the Foreplay III in for the flat rate repair service, and I will go through it and replace that board with the newer MJE-5731A's. 

If you're up for it, I can also build you a board that you can swap for your old one for less than the cost of the flat rate repair.

Otherwise, the MJE5731A's can go in the old board, with the metal tabs facing out.  It's a bit of a pain to get them in there, but is still doable if you're patient.

-PB

[jlharden]

PB, thank you for the prompt reply!

I may just take you up on the service. I'd take comfort in knowing that the unit is functioning as quietly and proficiently as possible. It's been a great piece of gear and has never failed to impress. Should I replace that popped resistor in the power supply board prior to sending it in or would you field that as well?

Thanks,
Jerrod

[Paul Birkeland]

I can take care of that for you as well, I wouldn't worry about it.  (Just leave a note in the box to remind me so I don't have to go hunting for why there's no B+ on one side)

-PB

[jlharden]

Great, I will do! So I just set up the service/return through the Bottlehead website and it will land in your hands? Any eta on turn around time? Thanks!

[Paul Birkeland]

Yes, we will mail you packaging materials and instructions.

Typical turnaround on kit repairs is about a week. 

-PB

[jlharden]

Excellent! Thanks for the prompt replies!

[jlharden]

Return box received today, but heavily damaged. I have used the enclosed packaging, but have another heavy duty box of similar size I will use. I assume the proper address for return is the 9415 Coppertop Loop NE, Bainbridge Island, Wa 98110 address?

Thanks,
Jerrod

[Paul Birkeland]

Yes, that will work.

Amazing that the box got damaged, considering there's nothing but packing materials in it!

Just to be sure, there shouldn't be any air space when you repack your Foreplay, and the box needs to be at least 12x12x12.

-PB

[jlharden]

Yes, thank goodness! I now have it double boxed for safe travel. Should land in your hands next week.

Thanks!

[Paul Birkeland]

I got your preamp all fixed up today. The center board was reasonably well cooked.

We'll get this out later this week after some burn in time.

-Paul

[jlharden]

Good deal! I'm also going to work on getting the noise level as low as I can. I'm sure the old Brimar tubes aren't helping but they seem to sound good! Any tips or tricks are appreciated.

Thanks!
Jerrod

[Grainger49]

There are a number of stickies under Legacy Products/Foreplay III on the board.  There is one that suggests a bypass cap on the regulator board for the Cathode Follower stage of the FP III Extended.

[Paul Birkeland]

Good deal! I'm also going to work on getting the noise level as low as I can. I'm sure the old Brimar tubes aren't helping but they seem to sound good! Any tips or tricks are appreciated.

What does the rest of your system look like?  I notice that you have the regulator bypass caps, and custom input padding.  (Or, how many SW clicks do you end up using?)

I can do a quick check of the noise level of your tubes vs. a known good set, just to check that off the list.

-PB

[jlharden]

The FPIII feeds a Marchand XM-44 active crossover splitting frequencies to a pair of Paraglow II's on horn loaded AMT drivers and Quicksilver Horn Mono amps powering Acoustic Elegance TD15 bass drivers. The second outputs feed a Driverack 260 DSP unit splitting signal to an array if sub-bass cabinets. The high frequency drivers are 105 db 1w/1m. System is much quiter with the solid state preamp that is in place, but that is to be expected. I do use the entire range of volume control and the inputs have been padded to equalize volume with the digital and analog sources.

Thanks,
Jerrod