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1964 Fisher Ambassador

There isn't a kit for these. The two 3000uf 35v should be replaced along with any other electrolytics underneath. Stay with modern equivalents for the stock values. ie: 3000uf would now be 3300uf. You can get single caps and stuff the can's. They must stay isolated from the metal chassis as they are part of the voltage doubler circuit and NOT GROUNDED like normal can caps. The caps have a cardboard sheath over the can to keep you from getting zapped by the fairly high voltage on the body of the caps. Once you stuff the guts and rewire them so the external can is not "Hot" the cardboard is not so much a requirement, altho you'd be better off leaving them alone.

You have 2 choices for the metal cans as they are kind of oddball values and voltages. 1.) Use Nichicon Pencil(UCS series) caps and stuff the can's or 2.) send the values/voltages of each can to Hayseed Hamfest. Don't do the 3000uf singles, just stuff them. www.hayseedhamfest.com

Search re-stuffing Can caps on Audiokarma if you've never done it or seen it done.
 
Fuses F1 through F4 being good is good news. This is an indication that the unobtanium germanium output transistors are probably ok. DO NOT TOUCH bias pots P1 through P4. If they momentarily go open during adjustment due to being dirty, the game is over. I do have a lengthy procedure for safely dealing with this, either by cleaning, testing, and adjusting the original pots out of circuit, or by replacing the bias network.

The 3000 µF 35 V capacitors should be upgraded to 50 V or higher. The 32 V on the schematic has a 10% variance which puts you at 35 V and todays line voltage is higher. Raising capacitance will not hurt either. My 600-T uses almost the same power amplifier and now has 10,000 µF 100 V capacitors with no problem. The reason for such a high voltage is I needed replacements that would fit the same clamps and holes, so physical dimensions were as important as values.

You can use a small capacitor in series with headphones at one of the secondaries of the driver transformers to determine if everything is good up to that point.
 
NO! They fuse the + and - legs of the amplifier, and you need that load to take accurate voltages.
 
Hey everyone.. Well I now know for sure that the issue of no sound was in the amp itself. The extra 690 amp I bought arrived today so I hooked it up to my variac and started with about 60 volts then slowly brought her up to 115 volts and wa la music. So now I can concentrate strictly on the original amp and get it re-capped.

I do have a question about the woofers in the Ambassador. Someone had made a commit on another forum that the woofers would need re-foamed. I thought in the early 60's it was either paper or rubber surrounds that was being used. Oh well I guess I will pull one and have a look at it so I'll know for sure.

Thanks again for everything. I'll be in contact.
Terry,
 
99.9999999994% sure that the surrounds are rubber impregnated cloth. You don't have to remove the spkr, just touch the back of the surround roll with your finger. It'll either be sticky (from the rubber sealant) or not.which is usually a paper edged surround. FISHER didn't start using foam based spkr surrounds until the mid 70's when they stopped making spkrs in the US and went to Japan.

As far as the amp goes, it's most likely in the power supply. Did you meter the fuses (F1thruF4)??? Or just do a visual. Metering will be pretty much 100% correct. Visual is about 80% accurate, as you can miss a filament that breaks at the end of the filament inside the end caps. You didn't say before, and I'm presuming you tested them visually.
 
I did meter the fuses. I do have a couple more speaker questions. First, do the crossovers usually need attention on these older Fisher consoles? Second, does the nine pin molex speaker plug on the amp need reworked if it's going to be used as a standalone amp?

Terry
 
The crossovers only need work (caps) if you are going to use as a console.

The Molex doesn't need to be reworked if you plan on using the speaker selection switch as designed. IIRC the switch is on the front panel of the tuner/preamp. If it's going to be stand alone, with no chance of going back in the cabinet, then get rid of the molex and install banana jacks or your favorite connector. You could rewire the EXTERNAL SPKR screw connectors to handle the speakers direct. Pins 3 and 9 are your LEFT(3) and RIGHT(9) speaker output's. FISHER has a BOLDED recommendation of NO LESS than 4ohm for external speakers on the schematic. I'd play it safe and use 8ohm speakers.
 
With two amps I've got to much on my plate. The extra amp will be a backup for the console, At least for now. I did take some voltage reading on the 12ax7's they were as followed. On the tuner side excluding the MPX pin 4 read -11.32dc on all, the AX7 on the amp 6.7dc.

Also, any suggestions on crossover caps or just stay with the same values?

Terry
 
Just concentrate on one amp. Recap the working one right now to get a good working knowledge of the unit. If you haven't done one of these before, I'd test after every part or every 2 or 3 parts. That way if you goof you only have a maximum of 3 parts to check. Once you get it finished then you have a rehabbed unit to use as a comparison for the non working unit. Also with a rehabbed unit the circuit voltages will be more in line with the schematic voltages.

Stay with the same values on the x-over caps.

The DC heater is a little high, but that could be because of your shore power voltage. If you have a variac, hook the console up to the variac and set for 117vac. This is your test setup for nominal voltages on the schematic. Also on the schematic there are notes for different types of voltages. Some are done with FM on, some not, etc. If your voltages are within 10% of nominal (>5% or <5%) you're ok.
 
Good Morning to All... I disconnected the wires from the main filter cap last night (60/40/40/40) I checked each leg with my capacitor checker and got the following results. 60 was reading 107 and each of the 40 legs read 73, just a little out of tolerance wouldn't you say. Anyway I'm still working on a order for the new caps and when they come in and I get started on the re-cap I'll probably start a new thread on this. I'm very much a rookie at this so I'm going to have a lot of questions.

Terry
 
Caps drifing high as they age isn't so unusual. The bigger problem is leakage or high ESR. Leakage loads down the power supply, makes heat, and can make the cap blow up where high ESR just produces lousy filtering.
 
larryderouin said:
NO! They fuse the + and - legs of the amplifier, and you need that load to take accurate voltages.
Click to expand...

At no signal, the current draw of the output stages is on the order of 100 mA per channel, so, unlike a tube amplifier, the load will not drop the voltage much. Also, transistor amplifier power supplies are designed to put out several amps, unlike the several 100 mA of their tube counterparts, so the source impedance of the supply has to be quite low.
 
Hey Guys, I got the amp and tuner out and on the bench and everything hooked up except the speaker selector switch which is in the console. Even with the new amp that works it wouldn't produce any sound until the 9-pin molex connector was connected. So how do I jumper the 9-pin to get sound, or am I just going about this completely wrong? Remember I'm a novice at this stuff.

Terry
 
Pin 3 is your LEFT CHANNEL +. from the Amp
Pin 9 is your RIGHT CHANNEL + From the Amp
Pin 6 or a screw in the chassis is ground.

Pin 2 is LEFT CHANNEL Internal spkr + (Molex or WS-1 RCA JACK)
Pin 8 is RIGHT CHANNEL Internal spkr + " " " " " " " " " "

Pin 1 is Left Channel EXTERNAL SPKR +
Pin 7 is RIGHT Channel EXTERNAL SPKR +
ground to gnd or com

Jumper 3 to either 2 or 1 for LEFT CHANNEL +
Jumper 9 to either 8 or 7 for RIGHT CHANNEL +
Ground lead to gnd or com.
 
Hey Guys, Quick question, Would it be better to start a new thread on this topic since I've started doing some of the re-capping or just continue with this one?

Terry
 
Continue on. It makes it easier in the future in case someone else finds a 64 Ambassador and runs into the same or similar problem.
 
OK... Here I go.

I've changed out the 40/40/40/60 can, plus C7,C8 20uf 250v and C21,C22 200uf 35v electrolytic caps out of some of my caps I had on hand. Still no sound. I am having a very hard time getting steady voltage readings. I did get a steady reading coming off the 60uf can cap which was 169.5 which I believe is 180v on the schematic. When I tried reading the three 40uf's the scale was all over the place, it would slowly run up to 400v then start over, and over. So what am I doing wrong? Remember Novice, that's me.

I also have a question about the silicon rectifier. Is that something that also needs attention?

Terry
 

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These are DC VOLTAGES. If it was set to AC you may get voltages all over the place. Also with low batteries on the meter it will show erratically. Change the batteries and take the voltages again. Make sure the ground probe(black) is solidly clamped to the chassis. Then the red or + probe to the connection on the can cap. Insulate all but the extreme end of the RED PROBE to keep the "AW SHITS" down to a minimum.

Lets set some ground rules for reporting voltages. We need to know exactly what you are measuring and how. You are doing ok on part designations, but the voltages are only 1/2 there.
Following are examples.
DC voltages = 170vDC
AC voltages = 170vAC
DC Millivolts = 300mVDC or . 300vDC
AC Millivolts = 300mVAC or .300vAC

Multiple voltages use a vertical listing rather than running it on in a sentence. Makes it easier to decipher.

The more detailed you make the information, the better we can decipher the problems.

The voltages that were steady (C20D) is fine. FISHER Allowed 10% variance in voltages due to both component variance, and voltage. You're within 5-6% so it's ok.

Is the Bridge rectifier like the one's you see in a 400-500c-800c or is it 4 diodes in a diamond between 3 terminal strips. If it's 4 diodes, you can leave them for now. If it's a Siemens block against the side, change it.
 
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