A Reference 400 Restoration/Modification
- Thread starter dcgillespie
- Start date
kentuckycat
Active Member
Can anyone recommend a good source for a restoration kit for the needed parts? I've already ordered the can caps from Hayseed but that's the extent of it. I don't see anywhere on Jim McShane's website that he's selling anything other than Citation kits. I checked with Metalbone and he' done with putting kits together. There are people selling Fisher 400 kits on Ebay, but I have no idea of what the quality that I'd be receiving from them would be. Or if anyone has a bill of materials I'd could starting hunting down the parts myself. At this point I'd like to complete the standard restoration / basic modifications.
thanks, Jeff
thanks, Jeff
kentuckycat
Active Member
The first two items on this thread is what I'd like to accomplish.1. Standard Restoration Work &
2. Basic Modification Package. I'd order from Mouser if I could trust myself to not screw it up - which is why I was asking if anyone had a BoM for this. I know I need to redo the power supply. I can hear it. I believe I need to work on the phono stage, too, because it doesn't seem to give me anything but a loud hum. I'll email McShane and see if he can set me up. Thanks.
I 2nd that McShane should be contacted to get the parts kit list for the 400.
kentuckycat
Active Member
Bruce, Tone, You were spot-on. I emailed Jim McShane and he wrote back just about instantly. I'm all set. Thank you!
bolero
Super Member
This thread is a great resource!
I have a 400 and have been planning to do the upgrades: I stopped using it when I read about the potential problems of unmodded use, but have been tempted to fire it up occasionally. I just checked the serial # and discovered it's an early model, so not as susceptible to issues compared to the later ones. Good news!
I have a 400 and have been planning to do the upgrades: I stopped using it when I read about the potential problems of unmodded use, but have been tempted to fire it up occasionally. I just checked the serial # and discovered it's an early model, so not as susceptible to issues compared to the later ones. Good news!
kentuckycat
Active Member
Happy New Year! I’ve received my Hayseed caps and my restore kit from J.M. I’ve studied the schematic quite a bit and I think I’m just about ready to go. Just one question that I’d like to get your opinion on. I was sent four 1k resistors for Screen Stability instead of 100Ω. I asked about this and it was explained to me that it was “because the modern 7868s tend to draw more plate and screen current than the old stock tubes did”. I have the original Fisher tubes. Should I ignore and buy some 100Ω or just install the 1k resistors? Or split the difference and get something in the middle? Does the difference matter?
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Empirical Data point. I have 2 400's (one early and one late), 2 800c's (1 10000 series for the '63 Executive and a standalone 35000 series) and a Sansui 1000A all using either EH7591's, Tungsol Re-Issue 7591's or in the case of the 400's EH 7868's. In all 5 I've put in Dave's recommended 100Ω screen stab resistors for the last 10 years. I've rebuilt at least 11 400's, a few other 800c's an all got the 100Ω resistors. No failures, no problems. With original tubes, it's your decision. But I'd read Dave's article here......http://www.tronola.com/Gillespie2544.pdf. and use your own judgement.
kentuckycat
Active Member
That’s all I needed. Thank you. Onward!
kentuckycat
Active Member
My 400 was only slightly modified by a previous owner. From what I can tell, the only changes were resistors in the filter section, one cap on the balance pot that’s way off spec’ and the balance pot itself that’s the correct value but seems to have different center point than the original (and the shaft is too long). The one thing I cannot understand is how this big glob of solder at a 182v junction never shorted against the chassis. The distance is < the thickness of printer paper.
The 3 giant ceramic resistors on the left are supposed to match the one on the right but they’re way different. I hope I’ve caught everything!
The 3 giant ceramic resistors on the left are supposed to match the one on the right but they’re way different. I hope I’ve caught everything!
Sub space force field.
kentuckycat
Active Member
I finished a basic restoration of my late model 400 last night. All of the can caps were replaced and 4 bags of resistors and caps that Jim McShane sent. I was slow and methodical swapping out the parts and as it turns out, the dim bulb stayed dim and music started playing as I slowly cranked the variac. What a great feeling. Next I’ll check voltages and add the bias pot that Jim McShane also included in his package. Someday down the road I will install the EFB™. Question. Should I remove the noose resistors now or wait until I install the EFB™?
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kentuckycat
Active Member
It reality threw some cold water on my enthusiasm when I realized only the right channel is working. That one channel sounds very nice, tough, so I’m guessing that I only have a small goof-up hiding in there somewhere. There was only one clue; I believe I heard the left channel working for a few seconds and then turned off. No arcing, no smoke, no pop, no drama. I checked the non-original balance pot with my ohm meter and it seems to be fine (except that the center of the resistance and the center of the D shaft's operation are about 15˚ off center of the centering pin. Prior to surgery, the balance worked except for the center issue. I loosened the pot, bent the center pin out of the alignment hole, reoriented the pot and retightened the nut. Seems like it will hold fast. Here's what I've done so far. Used DeOxit on all mechanical parts. Wiggled the tubes in a rotational pattern. Did the chopstick test but didn't find anything. I changed the L speaker to the R. It's the amp, not the speaker or cable. Does anyone have a run-through list that could help me isolate the dead channel problem? Thanks, Jeff
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kentuckycat
Active Member
Well, I found it. Even though I drowned the Speaker Off switch in DeOxit, it was that scratchy old switch that was the culprit. When I touch it I had stereo.
kentuckycat
Active Member
thornev
Super Member
A CL80 will get very hot. It is soaking up amperage. If you believe (and some better qualified can chime in) that it's too hot, perhaps you have an amperage issue. Depending on where you put the CL80, check voltages in the circuit preceding the CL80 to ensure your voltages are normal per the schematic.
kentuckycat
Active Member
I installed a bias pot and set it for the tube with the highest current to 40ma measuring across the new 10 ohm cathode resistor. Here’s what I’ve got;
V14; 27ma
V15; 29ma
V16; 40ma
V17; 26ma
These are the original Fisher labeled 7868 tubes. Does anyone have a recommendation for my next move?
Thanks- JC
V14; 27ma
V15; 29ma
V16; 40ma
V17; 26ma
These are the original Fisher labeled 7868 tubes. Does anyone have a recommendation for my next move?
Thanks- JC
kentuckycat
Active Member
The smell of electronics roasting is what had me alarmed, I think. After a while whatever was coating that CL has burned off and doesn’t smell so much anymore. I later learned that the CL series limiters have an operating temperature range of -58°F to +347°F.
So 222°F is just loafing!