Discussion in 'Fisher' started by moondogtn, Oct 10, 2017.
Looks great moon! Compared to the mess you've started with, you're really on your way!
Dave, I am trying to work on this as time permits. It was a long weekend but I did finally get transformer soldered in and got rid of the old pigtails. Much cleaner look! I took a couple of pics just to show the progress.
Also, did a little cleaning up of chassis. I will try faceplate soon.
What are other requirements/recommend items? Btw, I haven’t listened to it but hope to get to this week.
1. Frako caps (cathode bypass caps)?must be replaced, correct? I think there are 6. Any specific recommendations?
2. I still need to do basics such as deoxit controls.
Nichicon UKL's. Low Noise. Radials so you might have to do some creative lead lengthening. You could use Nichicon TVX series also. Not as low noise but orders of magnitude better than the Frako's, and they are axials. Replace them all, and look at the ends on the FRAKO's. If they have rubber ends, most likely they'll be bulged out.
If those Frako's are the same as found in the CX2, then check into the "Little Lytic" TE1100. 50uf @ 6v. Mouser got them in as "new." Nice and small, axials, and 105.* A little pricey but hey.......
Larry and notdigital, I see these below that are 25uF and 16 volts axial lead. I don't see any notes about being low noise?
The UKL offers a 22 or 33uF rated at 16 volts as well. I am sure either would be fine but assumed axial would be a little easier to install and look cleaner.
Almost forgot about the brown mylars...do those "need" to be replaced? I measured some and they seem ok but if prone to failure, do all need replaced?
Also, deoxit question. Should I mess with level(brass pots) As of yet, I haven't messed with those.
22uf is fine. If you can get the 25uf or 27uf even better. I'd bump the voltage up to 25V tho. Even tho they are bypass caps, they can be affected by today's higher voltages.
They should. They can go intermittent, or the leg can just pop off internally. I've seen both. Those are commonly called "Dog Turds".
DeOxit won't hurt them. Just make sure you back up the D5 with at least Faderlube, or Shield to replace the old lubricant that DeOxit D5 washes out.
I found the vishay/Sprague TE series with axial leads 25uF in both 16 and 25 volts at newark on sale for about a buck each so I ordered those to replace pink Frako.
I’ll get those installed and then power up and try to listen to it.
I will order Mylar replacements.
Those look like they will be fun to get to, especially the smaller ones.
Any other areas of concern that I should address?
Just being cautious really but wanted to ask.
Other than checking that the big .68 uF caps (typical value) don't have any DC leakage, that should be about it. Early stereo models using this cap from Fisher often showed they had significant DC leakage. The other film caps in the unit are usually fine. Boy, has this things come a long, long way from when you first started!!
Yeah. 2 pages ago it was a train wreck. I think he disproved "you can't get silk out of a Sow's ear.".
It’s getting there, thanks to y’all. I think those large two caps toward rear of unit are 1uF and the four large caps toward front are .47uF.
They showed to be correct capacitance with a cheap cap tester.
I began to replace the Frako caps last night. Those measure way off, like 150uF. I was planning to use 25uF 25volt TE series axial leads from Sprague. I may need to go with smaller value 25uF 16volt (which I already have) as I was having trouble finding a place to physically install. I will look at it again today as it was late so I may have been over complicating it. I will most likely just get these six caps replaced and listen to it before changing anything else.
Again, I truly appreciate all the help and encouragement. Thanks
That was my experience in my CX2. Stock value was 50uf; they were all coming in at between 95 and 130uf!! Only one was "acceptably" high at 65uf!
And if you think Frako's are bad, Ducati caps are even worse.
Ducati! Great bikes!
Hahaha. The lowest I measured was 125 uF. I finished installing the caps. Not the prettiest, by any means but, I am going for function not fashion. I powered up on DBT and all seems fine. I will test it out tomorrow and hopefully hear her sing.
Anything else I need to check prior to doing that?
So, I went ahead and tried it out. I am getting sound although very faint. No switches seem to make a difference. I will attempt to clean sockets again.
I did take voltages. Dave, I know we talked about using a dropping resistor to manage voltage but I actually forgot about it. I will need to install one as all my voltages off the HV side seem high.
These readings were all taken with chassis as grountd and DC unless otherwise noted.
Soldered to center?
C45 A 449
C45 B 402
C45 C 360
C45 D 311
C46 A 30.4
C46 B 23
C50 A 270
C50 B 235
C50 C 270
C50 D 235
I hope the format is ok. I see some that I may go back and double check but wanted to see what thoughts were. Thanks and I know it is Easter weekend so no rush of course.
Good job Bill. I would consider implementing the following:
1. Replace R93 with a 4000Ω 10W resistor to bring the voltage at the 345 volt point in line. C45-A should now be ideally rated for 500 volts.
2. Add a 1Ω 5W resistor to the AC heater/indicator lamp transformer winding, between the lead that is currently grounded, and ground. This will tame the 7 volts you are currently showing from that winding.
3. In your case, I would not add a primary winding resistor as I recommended with the stock transformer, as your DC heater voltages appear fine. Adding a resistor here to tame the B+ and AC heater voltages would drop the DC heater voltage unnecessarily. The expedients above will take care of those voltages without dropping the DC heater voltages any.
Wow, Dave. How cool it is to read about your figuring out these things. I'm reading several books and I'm beginning to understand how certain components are used to "tame" behaviors in electrical circuits. Reading posts like yours right above, it's becoming clearer why your recommendations work. Thorne
Dave, thanks, that all seems logical so now I will need to order parts.
Any recommendations for resistors, wirewound?
1. That can cap is only rated for 450 volts.
No thoughts on minimal volume issue? I did deoxit tube sockets again but haven’t tested since doing so I will try that and report back.
Hi Bill -- Sorry about missing the minimal sound issue, so again, a couple of comments:
1. If your filter cap is only rated at 450 volts, then a better way to go would be to leave R93 at its original value, and now add an additional resistor between the output of the rectifier tube (pin 3) and C45-A/R93. The exact value will need to be determined by trial and error as it cannot be calculated with simple Ohms Law -- but the value will likely fall into a range of 250 - 500Ω +/- and should be rated at 5W or more. The resistor's value should be determined so as to produce 390 vdc (or close to it) at C45-A. That way, you won't have to change out C-45 if section A is in a new can you had made or bought.
2. As for the little to no sound, make sure that the dummy plug is installed into the Remote Control socket on the rear of the chassis. It is required for there to be any sound produced from the unit if the actual remote control unit is not connected. Sometimes these will be missing. If so, there will be no sound, and you will need to install the appropriate jumpers at the socket inside the set to emulate the missing dummy plug. If needed, the jumpers should be connected between pins 1&3, and between pins 6&8.
Let us know!
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