Bottlehead Forum

Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: Laudanum on July 21, 2011, 04:10:27 AM

Title: PS Resistors, Caps, FP III
Post by: Laudanum on July 21, 2011, 04:10:27 AM

If it's not giving too much away, can someone tell me the value and wattage rating of the cement/wirewound resistors used in the stock FP III. 

Also, I think I read that the output caps are 2.2uf, if thats correct, Im set there.   But would a capacitor upgrade on that OD3 regulator socket make any sonic difference?  If so, what is the value and voltage of that stock cap?

Doing a parts order for upcoming build.

Thanks kindly.

Title: Re: PS Resistors, Caps, FP III
Post by: Paul Joppa on July 21, 2011, 05:15:36 AM

The parts are described in the manual's parts list.

The large resistors feeding the 0D3 are 20K, 10watt. They are in parallel, so a 10K 20 watt (or greater) resistor would work equally well. The resistors are rated for much more than the actual power dissipated, in order to reduce the resistor temperature, but they still get pretty darn hot. Make sure the any new or different resistor(s) are able to dissipate that heat.

The 0D3 cap is rated 0.1uF 630v. When the circuit was being developed, we tried a 0.056uF teflon cap (Russian mil-spec surplus) which was an audible improvement. The maximum capacitance is 0.1uF according to the 0D3 spec, and it becomes less effective the smaller the value used. I would stick with a 600v minimum rating - it normally operates with only 150v, but if the 0D3 is removed of dies then it will see the full power supply voltage and the initial transient before the other tubes start to conduct will be pretty high - 500v or so.

Title: Re: PS Resistors, Caps, FP III
Post by: Laudanum on July 21, 2011, 11:50:49 AM

Thanks Paul.  I have Seduction and FPIII kits are on order, Im awaiting shipment so I have no manual available.  Just wanting to get a jump on those few passives.

Title: Re: PS Resistors, Caps, FP III
Post by: Laudanum on July 23, 2011, 02:41:51 AM

Paul (or anyone else) ...  There appears to be a smaller cement/wirewould resistor that I missed, looks like a 5 watt Xicon.  What's the value of that one?

Thanks.

Title: Re: PS Resistors, Caps, FP III
Post by: Lee Hankins on July 23, 2011, 06:56:23 AM

The FP III parts list I have shows 3 different wirewound resisters: one 0.62 ohm 5W; one 2.7K ohm 5W; and two 20K ohm 10W.

Lee Hankins

Title: Re: PS Resistors, Caps, FP III
Post by: Laudanum on July 23, 2011, 09:51:03 AM

Thank you, Lee.