Still All About The "IBAM"

P

PShuff

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Hi! :banana:
I've asked questions about this in several places now, so many I'm losing track!
I think this has been clarified by Mr. Bolce, but it was in the 800-C thread and the part numbers are different, so we are a wee bit apprehensive about our understanding!
When we install the IBAM in our Fisher 500-C, will we be removing R131, R132 AND C86?
I hate to be a pest, but the details on this mod are in so mnay places I can't keep track of it all and that's made all the more difficult by just barely feeling at home with all this!
Thanks guys! :banana:
Phyllis
 
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This was Mr. Bolce's post that got us confused:
"Did you put the four 33uf caps in? Did you remove the original electrolytic cap? These caps are very important for suppressing the 180hz hum. If you left in the old cap, did not install all four caps, attempted to use one big cap, or put one big cap in the wrong place you will get hum."

Which electrolytic are we talking here?

From this thread, post #20:
http://www.audiokarma.org/forums/showthread.php?t=394064&page=2

Thanks again for being kind!
Phyllis

P.S.: This is what we built for our 500-C. Our R131, R132 and C86 are still like factory (except the C86 is a new part) R132 is connected to the board between C10 and C11 on the new board
http://www.quadesl.com/pdf/500c_capboard.pdf
 
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REMOVE C86-R131-R132. The IBAM replaces these with the 4 resistors(R131) and 4 caps(C86) on the board, and the 4 trimmers(R132). (The parts in parentheses are the parts replaced by the new individual parts). Connect the input lead to the old wire or the bias cap NEGATIVE LEAD (C-97A&B).

The output of each tube setup attaches to the 200-220K(in YOUR CASE 180K) where the old bias leads attached. If two of the 180K resistors are connected to each other (1 lead does) separate them and connect 1 lead to 1 resistor. Mark each trimmer with a blk marker.

Larry

EDIT: 15 minutes later: I forgot you had the Stokes board in it. I don't know enough about the Stokes board to say for certain. I would correlate which ever cap and resistor on the board that replaced C-86-R131-r132, and possibly remove them?? I would think that removing the cap/resistors on the board and connecting the IBAM input to the -(neg) side of the bias caps would give the same effect as removing C-86-R131-R132.

SOMEONE else with this setup want to Chime in????? PLEASE?!?!?!?!!?!?!?!!!!!!!!!


Larry
 
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larryderouin said:
REMOVE C86-R131-R132. The IBAM replaces these with the 4 resistors(R131) and 4 caps(C86) on the board, and the 4 trimmers(R132). (The parts in parentheses are the parts replaced by the new individual parts). Connect the input lead to the old wire or the bias cap NEGATIVE LEAD (C-97A&B).

The output of each tube setup attaches to the 200-220K(in YOUR CASE 180K) where the old bias leads attached. If two of the 180K resistors are connected to each other (1 lead does) separate them and connect 1 lead to 1 resistor. Mark each trimmer with a blk marker.

Larry

EDIT: 15 minutes later: I forgot you had the Stokes board in it. I don't know enough about the Stokes board to say for certain. I would correlate which ever cap and resistor on the board that replaced C-86-R131-r132, and possibly remove them?? I would think that removing the cap/resistors on the board and connecting the IBAM input to the -(neg) side of the bias caps would give the same effect as removing C-86-R131-R132.

SOMEONE else with this setup want to Chime in????? PLEASE?!?!?!?!!?!?!?!!!!!!!!!


Larry
Click to expand...

Hi Larry! :banana:
You must have missed my "P.S." in the post above!
"Our R131, R132 and C86 are still like factory (except the C86 is a new part) R132 is connected to the board between C10 and C11 on the new board"

That's why I included the link to the board's layout. The board just feeds the original wire and resistors and that little cap the way Fisher made it (you don't change that when you put in the board).
What's throwing me is that post I quoted where Mr. Bolce asked another poster if he had removed an electrolytic? Still don't know what he meant about that one?

I think you have us on track here! :banana:
Thank you Larry!
Phyllis
 
larryderouin said:
REMOVE C86-R131-R132. The IBAM replaces these with the 4 resistors(R131) and 4 caps(C86) on the boardLarry
Click to expand...

Understood! :banana:
If you don't mind, and you can make it simple enough for me to understand, why/how do we go from just a little .1uF cap to 33uf?
Anything to do with stability maybe?
(I just barely have learned how to solder! :yes:)

Thank you again Larry for being so kind!
Phyllis
 
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The .1 is directed to ground(old C86) . The 33uf in the IBAM are for stability in the circuit . The resistors are changed in that each one is only handling one tube instead of 4. I'm not real good on the math and all. I just know it works. I've done this on 3 different units (1 a sansui 1000A) and haven't had problems with any of them.

Drew or one of the guys with a lot more theory than I should be able to answer the cap question.

Larry
 
If you don't remove them the bias is wrong, I removed them when I did the sds board and the bias board. I believe we are talking about the 2 resistors and single cap that are wired to a terminal strip that feed bias, directly underneath the sds board.
 
bktheking. That's correct. However the question is how did we go from a single .01uf to 4 33uf caps.
 
Let me apologize for being a lurker. This is the first time I have had in weeks.

The cap in question is in the 500b, 500c, 800b and 800c. It is a 0.1uf (not 0.01uf) cap. It is not present in the 400. In the thread referenced the concern was leaving the 100uf cap that is used in the 400, creating an excessive total value for the filter.

A little history. When working on the IBAM I noticed that the 400 design was different than the others. I also saw that the 400 was the last of the series that Fisher designed (in some obscure thread I can't find now).

I tried the 400 design in my 500c and noticed that an annoying 180hz spike practically disappeared.

I designed the IBAM with this in mind. The four 33uf caps provide a total value of 132uf.

At this point I would say to leave the 0.1uf cap if it is there. It won't hurt anything and I like to do as little harm as possible.

I posted http://audiokarma.org/forums/showpost.php?p=5117229&postcount=49 showing how you can hook up a computer soundcard to look at the 180hz spike if you are interested. BTW, the thread was about volume pot channel imbalance which you can check with this setup.
 
drewbolce said:
Let me apologize for being a lurker. This is the first time I have had in weeks.

The cap in question is in the 500b, 500c, 800b and 800c. It is a 0.1uf (not 0.01uf) cap. It is not present in the 400. In the thread referenced the concern was leaving the 100uf cap that is used in the 400, creating an excessive total value for the filter.

A little history. When working on the IBAM I noticed that the 400 design was different than the others. I also saw that the 400 was the last of the series that Fisher designed (in some obscure thread I can't find now).

I tried the 400 design in my 500c and noticed that an annoying 180hz spike practically disappeared.

I designed the IBAM with this in mind. The four 33uf caps provide a total value of 132uf.

At this point I would say to leave the 0.1uf cap if it is there. It won't hurt anything and I like to do as little harm as possible.

I posted http://audiokarma.org/forums/showpost.php?p=5117229&postcount=49 showing how you can hook up a computer soundcard to look at the 180hz spike if you are interested. BTW, the thread was about volume pot channel imbalance which you can check with this setup.
Click to expand...

Hello! :banana:
Yes, and I have corrected my post to say .1uF NOT .01uF!:no:
So just to absolutely understand what you are telling me I can disregard the comments regarding an ELECTROLYTIC as it in no way applies to our model receiver the 500-C.
Yes?
As for the new .1uF we installed, I can't remember 100% right now as the receiver is currently assembled and playing, but it would do no harm either way to leave it in, OR out?
I only ask this (again) as I believe we are going to have to unsolder it to get it out of the way and free up the white bias wire.
To re-cap (no pun intended! :) ) we just have to remove R131, R132 and C86 and take that wire coming off the Stokes board and feed the IBAM with it.

Anything need to be done about how it feeds the heaters on V14, V15, V16 and V17?

For the purposes of trying to understand (learn) are the heaters on those tubes fed with negative voltage? And how does it drop from the "-22V" to the 12.6 MAXIMUM that is on the tube data sheet for the 12AX7 heaters?

Thank you Mr. Bolce and thank you too Larry! :banana: for your ongoing patience! :yes:
You guys are wonderful!
Phyllis
 
drewbolce said:
Let me apologize for being a lurker. This is the first time I have had in weeks.

The cap in question is in the 500b, 500c, 800b and 800c. It is a 0.1uf (not 0.01uf) cap. It is not present in the 400. In the thread referenced the concern was leaving the 100uf cap that is used in the 400, creating an excessive total value for the filter.

A little history. When working on the IBAM I noticed that the 400 design was different than the others. I also saw that the 400 was the last of the series that Fisher designed (in some obscure thread I can't find now).

I tried the 400 design in my 500c and noticed that an annoying 180hz spike practically disappeared.

I designed the IBAM with this in mind. The four 33uf caps provide a total value of 132uf.

At this point I would say to leave the 0.1uf cap if it is there. It won't hurt anything and I like to do as little harm as possible.

I posted http://audiokarma.org/forums/showpost.php?p=5117229&postcount=49 showing how you can hook up a computer soundcard to look at the 180hz spike if you are interested. BTW, the thread was about volume pot channel imbalance which you can check with this setup.
Click to expand...

Hi Mr. Bolce!
I forgot to post this link in post #2 above. I have added it now.
http://www.quadesl.com/pdf/500c_capboard.pdf
Would you please take a look at it for me and confirm that we will be simply taking the wire that is attached at the pad between C10 & C11 (on the board) and feeding it directly to the IBAM, after removing R131, R132 and C86? Leaving in place of course the wire that splits off to feed the (4) 12AX7s?

Thank you very much! :banana:
Phyllis
 
Phyllis; Disregard anything pertaining to an electrolytic! Your's does not have one in this circuit.

1.) remove the R131, 132.
2.) leave the .1uf cap alone (pre drew's comments above.)
3.) Tie the IBAM INPUT to the white bias wire, and the .1uf. (think of a "T". The white bias wire is the Vertical part of the "T", the .1uf cap, one of the side cross pieces, and the IBAM Input the other cross piece.)

Nothing needs to be done to the heaters as the Heaters feed directly off the cap before the BIAS tap.

Think of the Heaters as resistors. (technically that's what they are).

In a series configuration, the current through all of the resistors is the same, but the voltage across each resistor will be in proportion to its resistance. The potential difference (voltage) seen across the network is the sum of those voltages, thus the total resistance can be found as the sum of those resistances:

Resistors in a parallel configuration are each subject to the same potential difference (voltage), however the currents through them add.
attachment.php

So you see 24V at the top of the group Pin 4 on V15 and V17. Then check pin5 on the same tube. It's now 12V! The resistance of the heater is sufficient to drop the voltage 12v or so. Now test pin 4 on V14 and V16 (same as pin 5 on V15-17). Then test pin 5 on V14-16. It'll show zero volts as it's a.) the tail end of a 12v drop, and b.) connected directly to chassis ground. So even tho it's 24V when you started, because you had multiple heaters in series (V14-15 and V16-17) that each had a 12v drop each, you get zero volts at the end. NO PROBLEMO.

Print this out and you can figure out all kinds of things pertaining to voltage, amps, watts, ohms. You'll need this for future rehab's/projects.

attachment.php
 

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larryderouin said:
Phyllis; Disregard anything pertaining to an electrolytic! Your's does not have one in this circuit.

1.) remove the R131, 132.
2.) leave the .1uf cap alone (pre drew's comments above.)
3.) Tie the IBAM INPUT to the white bias wire, and the .1uf. (think of a "T". The white bias wire is the Vertical part of the "T", the .1uf cap, one of the side cross pieces, and the IBAM Input the other cross piece.)

Nothing needs to be done to the heaters as the Heaters feed directly off the cap before the BIAS tap.

Think of the Heaters as resistors. (technically that's what they are).

In a series configuration, the current through all of the resistors is the same, but the voltage across each resistor will be in proportion to its resistance. The potential difference (voltage) seen across the network is the sum of those voltages, thus the total resistance can be found as the sum of those resistances:

Resistors in a parallel configuration are each subject to the same potential difference (voltage), however the currents through them add.
attachment.php

So you see 24V at the top of the group Pin 4 on V15 and V17. Then check pin5 on the same tube. It's now 12V! The resistance of the heater is sufficient to drop the voltage 12v or so. Now test pin 4 on V14 and V16 (same as pin 5 on V15-17). Then test pin 5 on V14-16. It'll show zero volts as it's a.) the tail end of a 12v drop, and b.) connected directly to chassis ground. So even tho it's 24V when you started, because you had multiple heaters in series (V14-15 and V16-17) that each had a 12v drop each, you get zero volts at the end. NO PROBLEMO.

Print this out and you can figure out all kinds of things pertaining to voltage, amps, watts, ohms. You'll need this for future rehab's/projects.

attachment.php
Click to expand...

Thank you Larry! :banana:
You are very sweet, and I mean that!
I don't want to this to sound the wrong way but I sure think the IBAM construction and installation along with an approved parts list would make a great sticky! :yes:
TONS about it here but it's all over the place!
By approved parts I mean ideal as if like someone were making an order not just making do with stuff on hand. OR what Mr. Bolce thinks is best. This is helpful if you aren't sure of the how and what to make substitutions and the like.
That would be very helpful to know nothings (like me) that can follow instructions but can't always "see" this kind of thing.
And it'd be a fantastic quick reference! :banana:
Don't want to come across as the snot nosed presumptuous new girl though! If I do please forgive!
Thank you Larry!
Phyllis
 
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Part recommendations are just that. Recommendations. People have their favorites as to what they'll use for parts. As long as the Capacitance, voltages, resistances, other specifications (electrically) are met or exceeded, you can use any brand you desire. Take the IBAM for example. My 1st one I made from parts from Radio Shack. The next two I made from parts gotten when I made an order from mouser using Nichicon, Bourns, other brand names. Seems crazy to get $5.00 worth of parts when the shipping is going to be $7.00.

You can recommend a certain part, but for every part out there, there are 10-20 equivalent parts at each distributor (mouser, digikey, parts express, etc.). And your favorite brand may not be the next guys cup of tea. So you see where the problems begin? It's like coupling caps. What is a good coupling cap for a 500-C? Some guys swear by Orange Drops, some guys K40Y russian's, some Illinois yellow axials, etc.,etc.,etc. So what you do is draw up a schematic, with a parts list of general specifications. The IBAM is listed in the Common replacement parts for FISHER's sticky along with Drew's drawing, and my photo's of my 400 and 800 modded.

Some guys build them on boards and attach them with stand-off's. BHAMHAM has built his using point to point soldering and mounting the parts on Terminal strips, with the trimmers sticking out thru the back of the unit thru the old power plug holes.

So even tho the idea has it's merits, the amount of documented modifications done and the different mounting methods preclude a specific method of building the IBAM and mounting it. I've shown how I did it as a general idea (in the sticky).
You might want to build your's differently.

Larry
 
larryderouin said:
Part recommendations are just that. Recommendations. People have their favorites as to what they'll use for parts. As long as the Capacitance, voltages, resistances, other specifications (electrically) are met or exceeded, you can use any brand you desire. Take the IBAM for example. My 1st one I made from parts from Radio Shack. The next two I made from parts gotten when I made an order from mouser using Nichicon, Bourns, other brand names. Seems crazy to get $5.00 worth of parts when the shipping is going to be $7.00.

You can recommend a certain part, but for every part out there, there are 10-20 equivalent parts at each distributor (mouser, digikey, parts express, etc.). And your favorite brand may not be the next guys cup of tea. So you see where the problems begin? It's like coupling caps. What is a good coupling cap for a 500-C? Some guys swear by Orange Drops, some guys K40Y russian's, some Illinois yellow axials, etc.,etc.,etc. So what you do is draw up a schematic, with a parts list of general specifications. The IBAM is listed in the Common replacement parts for FISHER's sticky along with Drew's drawing, and my photo's of my 400 and 800 modded.

Some guys build them on boards and attach them with stand-off's. BHAMHAM has built his using point to point soldering and mounting the parts on Terminal strips, with the trimmers sticking out thru the back of the unit thru the old power plug holes.

So even tho the idea has it's merits, the amount of documented modifications done and the different mounting methods preclude a specific method of building the IBAM and mounting it. I've shown how I did it as a general idea (in the sticky).
You might want to build your's differently.

Larry
Click to expand...

Hi Larry! :banana:
Understood, completely.
I was asking though more as to minimum specs and types.
Like what's best for a given use, a wire wound or a metal film, that sort of thing.
Mouser and the like can be overwhelming when you have 10, 20 or more bits with the same basic values but all sorts of little differences on the data sheets (which I don't have a clue about!)
Not so much brand recommendations, more like ripple, ESR and all that stuff, or if it even makes a difference, like in power supplies.
Advanced knowledge which I've read enough about in other threads and on other topics to know now that all these things can make a difference, just don't know the when and where.
Maybe I'm over thinking things!
Thank you Larry!
Phyllis
 
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http://electriciantraining.tpub.com/index.htm

Naval Electronic engineering training course
probably the best way is to start reading reference materials. NEETS is a good start. It's the successor to BE&E (Basic Electricity & Electronics) the course all personnel who had a rating having anything to do with electricity or electronics had to take before their primary rating school.
 
PShuff said:
Hi Mr. Bolce!
I forgot to post this link in post #2 above. I have added it now.
http://www.quadesl.com/pdf/500c_capboard.pdf
Would you please take a look at it for me and confirm that we will be simply taking the wire that is attached at the pad between C10 & C11 (on the board) and feeding it directly to the IBAM, after removing R131, R132 and C86? Leaving in place of course the wire that splits off to feed the (4) 12AX7s?

Thank you very much! :banana:
Phyllis
Click to expand...

I am a great fan of the Sheldon Stokes cap board. It does, however, have a serious design flaw.

Fisher went to great lengths to put the heat producing resistors in places where they would not heat sensitive components and were ventilated properly. This is why following the power supply section of the schematic and relating it to component placement can be difficult for the inexperienced.

The 15 ohm resistor (R142, R1 on the cap board) in the bias circuit is a real heater. I strongly suggest you use the original resistor (they almost never go bad) in it's original location. Of course, you do not install the resistor R1 on the cap board. Just run a longer wire from the resistor to the board. Solder it in where the resistor would go on the + side of the cap C11. Leave the connection from the resistor to the chassis in place.

I also suggest you mount R2 and R3 (both 3w resistors) to the foil side of the board about a 1/8" off the board surface. This will allow the heat to dissipate through the chassis vent holes, prevent board burning and help prevent cap heating.

The filament out wire pad you noted will go directly to the IBAM and the (4) 12ax7's. You can use the other open pad from R1 (ground) for the ground connection on the IBAM.

All other components of the bias circuit are removed (C86, R131 and R132). Remove or leave in place unconnected the old selenium bridge (CR6).
 
drewbolce said:
I am a great fan of the Sheldon Stokes cap board. It does, however, have a serious design flaw.

Fisher went to great lengths to put the heat producing resistors in places where they would not heat sensitive components and were ventilated properly. This is why following the power supply section of the schematic and relating it to component placement can be difficult for the inexperienced.

The 15 ohm resistor (R142, R1 on the cap board) in the bias circuit is a real heater. I strongly suggest you use the original resistor (they almost never go bad) in it's original location. Of course, you do not install the resistor R1 on the cap board. Just run a longer wire from the resistor to the board. Solder it in where the resistor would go on the + side of the cap C11. Leave the connection from the resistor to the chassis in place.

I also suggest you mount R2 and R3 (both 3w resistors) to the foil side of the board about a 1/8" off the board surface. This will allow the heat to dissipate through the chassis vent holes, prevent board burning and help prevent cap heating.

The filament out wire pad you noted will go directly to the IBAM and the (4) 12ax7's. You can use the other open pad from R1 (ground) for the ground connection on the IBAM.

All other components of the bias circuit are removed (C86, R131 and R132). Remove or leave in place unconnected the old selenium bridge (CR6).
Click to expand...

Thank you Mr. Bolce! :banana:
Very much! :yes:
Phyllis
 
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