(Topic ID: 234552)

Firepower System 6, no sound = bad transformer?


By lpnsocal

3 months ago



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  • 18 posts
  • 5 Pinsiders participating
  • Latest reply 3 months ago by pindel
  • Topic is favorited by 2 Pinsiders

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    asieg (resized).jpg
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    243B06BD-22CC-4645-9981-A383F8AA0D72 (resized).jpeg
    fp sound b2 (resized).jpg
    fp sound b installed (resized).jpg
    fp sb rear (resized).jpg
    front transformer (resized).jpg
    rear transformer (resized).jpg
    Power Wiring Diagram.pdf (PDF preview)
    FP Sound B.pdf (PDF preview)

    #1 3 months ago

    I'm trying to help a friend get his FP up and running, so I'm assessing the various issues to order parts etc. Since I have a FP I can/did swap boards as needed to narrow things a bit. I am at the last issue(hopefully) and it exists with his original and my sound board installed. For the record continuity was checked connector to speaker and to volume control. I also plugged in a different speaker for S... and giggles. Otherwise, the game seems to play as it should w points scored, solenoids firing, etc.

    I checked the Sound board test point voltages(Voltage per manual)and got:
    TP1 10.99(12v),
    TP2-13.5(-12v),
    TP4- 5 (5)

    Then I checked the Connector 10J1 and got 9.6vac on both pins 1 & 9, schematic/manual says they should be 18.7vac. Pin 5 - 0 vac(18.7 vac c.t. tho I'm not sure what the c.t. stands for) So I then check Power Board 3P1 pin 12(gry/wht) and got 0 vac.

    Does this all mean a bad transformer is the issue?
    .

    FP Sound B.pdf
    #2 3 months ago

    Transformer usually look blown, burnt or melted if they are bad. Unplug the transformer from the power supply and test VAC from lug 18 (black lead) to 15 (red lead) you should get should 9.3 VAC. Then lug 18 (black lead) to 16(red lead). Once again 9.3VAC.

    If you don't get those reading check continuity between those lugs (with the machine off). If you are missing one you might have a broken wire. If it's broken near the lug you may be able to scrape off some of the lacquer and solder it back on.

    #4 3 months ago

    Hey Cheddar thanks for the direction. To be clear, you want me to unplug 3P1(the input to the power board) and then power up game and check the lugs' voltage. Correct?

    This is the diagram I was using, but I will check ou the link you provided too.

    Power Wiring Diagram.pdf
    #5 3 months ago
    Quoted from lpnsocal:

    Hey Cheddar thanks for the direction. To be clear, you want me to unplug 3P1(the input to the power board) and then power up game and check the lugs' voltage. Correct?
    This is the diagram I was using, but I will check ou the link you provided too.
    [quoted image]

    Yes, since the 12 and -12 unregulated are the only things that don't work we can verify them at the transformer.

    #6 3 months ago
    Quoted from lpnsocal:

    ...
    I checked the Sound board test point voltages(Voltage per manual)and got:
    TP1 10.99(12v),
    TP2-13.5(-12v),
    TP4- 5 (5)
    Then I checked the Connector 10J1 and got 9.6vac on both pins 1 & 9, schematic/manual says they should be 18.7vac. Pin 5 - 0 vac(18.7 vac c.t. tho I'm not sure what the c.t. stands for) So I then check Power Board 3P1 pin 12(gry/wht) and got 0 vac.
    Does this all mean a bad transformer is the issue?
    [quoted image]

    Your voltages and transformer are proper. Power from transformer is 18.7V Center Tapped or "CT". The center tap of that particular winding is tied to ground through sound board's J1 pins 4 & 5. This allows you to use the single winding from the transformer to create a dual AC supply -- half for the +12 and half for the -12.
    If you measure either one of the two outer legs of that transformer's output with the other lead of the meter to the center tap then you will get 18.7/2 or about 9.3VAC. Of course, this is unregulated so it's just a ballpark voltage measurement so your 9.6VAC is fine.

    #7 3 months ago
    Quoted from G-P-E:

    Your voltages and transformer are proper. Power from transformer is 18.7V Center Tapped or "CT". The center tap of that particular winding is tied to ground through sound board's J1 pins 4 & 5. This allows you to use the single winding from the transformer to create a dual AC supply -- half for the +12 and half for the -12.
    If you measure either one of the two outer legs of that transformer's output with the other lead of the meter to the center tap then you will get 18.7/2 or about 9.3VAC. Of course, this is unregulated so it's just a ballpark voltage measurement so your 9.6VAC is fine.

    Ed, Thanks for the info..., I think it's good news? Transformer good..., means sound issue somewhere else to be found. Tho I am a bit confused about your mention of pins 4 & 5, as they don't exist on my sound boards(10) J1. Per diagram in post#4 I have pins 1,5,9 being used. I was also going to do the test you mentioned about the center tap(c.t. mystery solved thx) but really couldn't tell if it is labelled or readily available(see pics, probe is where gry/wht goes in)

    Quoted from Cheddar:

    Yes, since the 12 and -12 unregulated are the only things that don't work we can verify them at the transformer.

    Cheddar, I am getting +12(TP1) and -13.5(TP2) so I didn't perform the test.

    Meanwhile.... I double checked the original speaker and got a nothing result, then tested the backup I placed earlier and got 7.3 ohms ,so I'll go with that's not the problem. Continuity from board to speaker and volume control all good. Other than the Center tap test, I'm not sure where to test now.

    front transformer (resized).jpgrear transformer (resized).jpg
    #8 3 months ago

    You've got good power so that's a good start.

    Did you recrimp the connectors on the sounds card? Reflow the header pins? The connectors are more likely since the problem stays with the machine and not the board.

    How about some pics of the sound board in question?

    #9 3 months ago

    I reinstalled the original board back into the game but before I did it I verified continuity to the first component from respective pin( including data ribbon.) So the short answer is "No" to the recrimping and reflowing. I also checked continuity to driver board and the respective drivers from 10-J3. I had previously checked the other connectors out to their destinations for continuity, so everything seems to connect as it should.

    The board/cards are actually pretty nice, nicer than my replacements.

    I think my next course of action is to install my machines complete head on this game and see what happens...

    Though that does sound like the act of a desperate man

    fp sound b installed (resized).jpgfp sound b2 (resized).jpgfp sb rear (resized).jpg
    #10 3 months ago
    Quoted from lpnsocal:

    ...Tho I am a bit confused about your mention of pins 4 & 5, as they don't exist on my sound boards(10) J1. Per diagram in post#4 I have pins 1,5,9 being used. I was also going to do the test you mentioned about the center tap(c.t. mystery solved thx) but really couldn't tell if it is labelled or readily available(see pics, probe is where gry/wht goes in)

    [quoted image][quoted image]

    Typo on my post -- should have been pins 5 and 6, not 4 and 5.
    On sound board -- pins 5 and 6 are both connected together. That diagram uses pin 5 but could have just as easily used pin 6.

    Solder tabs are not exposed for wires 15, 16 and 18 on that transformer so difficult to measure there. To see full voltage - measure between pins 1 and 9 on sound board with connector installed. To see tap voltages (half voltage) - measure between pins 5 and 1 for one tap and measure between pins 5 and 9 for second tap. However - since you measured +12 on TP1 and -12 on TP2 then there is nothing wrong with the AC voltage getting to the board and BR1 on your sound board is OK. And IC8 (7805 voltage regulator) is also working fine since you got 5V on TP4.

    So... now what I don't see described... what is actually happening to the sound board? No sound at all?

    If no sound, that is difficult to tell with just a meter. First place I would look is J4 connection to volume control but to do this really requires an oscilloscope. I would follow sound from connection near W1 through R11, R12 and wrapped around to C12 and see if the signal disappears or not.

    #11 3 months ago

    break the board into three section. the power supply (i think you have checked this is OK). The CPU. The analogue stuff.... check through in that order.

    The CPU, see if reset is high (p40). external clock is going (p37). When you push the diag button the PIA ports connected to the DAC 1408 should begin to pulse. In game play mode the PIA ports going to the DAC should also go active when you trigger sounds.

    Introduce noise through the amplifier to check to see if it is likely working. Just twizzling the pot if you get some cracks, pops, and hum is a pretty good sign. When the sound board is connected to the speech card the analogue sound first goes across the ribbon to mix in with speech and goes through the 1458 op amps then back across the ribbon again. A bad 1458 can produce no sound or speech.

    Common issues... I see and AMI brand CPU chip in a possible scanbe socket. So you have an unreliable chip in an unreliable IC socket... double whammy.

    The ribbon cable gets screwed up from the tight bends. It looks like you have the type you can attempt to press down a new ribbon into... last resort to do that... make sure you are sure the ribbon is broken before trying because it does not always end well.

    Not uncommon for the 1458 op amps on the speech board to be blown.

    #12 3 months ago

    I thought we had established this sound board works in another firepower. Is that correct?

    #13 3 months ago
    Quoted from Cheddar:

    I thought we had established this sound board works in another firepower. Is that correct?

    Incorrect, No Sound Boards work. Originally an alternate FP sound board from a working(prior to going into storage)game placed into project machine, along with other boards as I move along in diagnosis of game issues. Once I saw I had power board issues, I swapped for another in order to continue tests, so I could order all needed parts from Ed in one try. With the alt power board in, game plays etc..but no sound at all. No speaker buzz, nada.

    Quoted from G-P-E:

    Typo on my post -- should have been pins 5 and 6, not 4 and 5.
    On sound board -- pins 5 and 6 are both connected together. That diagram uses pin 5 but could have just as easily used pin 6.
    Solder tabs are not exposed for wires 15, 16 and 18 on that transformer so difficult to measure there. To see full voltage - measure between pins 1 and 9 on sound board with connector installed. To see tap voltages (half voltage) - measure between pins 5 and 1 for one tap and measure between pins 5 and 9 for second tap. However - since you measured +12 on TP1 and -12 on TP2 then there is nothing wrong with the AC voltage getting to the board and BR1 on your sound board is OK. And IC8 (7805 voltage regulator) is also working fine since you got 5V on TP4.
    So... now what I don't see described... what is actually happening to the sound board? No sound at all?
    If no sound, that is difficult to tell with just a meter. First place I would look is J4 connection to volume control but to do this really requires an oscilloscope. I would follow sound from connection near W1 through R11, R12 and wrapped around to C12 and see if the signal disappears or not.

    Ed, I think you are saying that if I had something more than a MM and logic probe I might be able to work backwards on the sound board(not card) and find where the signal ends, Correct?

    Quoted from barakandl:

    break the board into three section. the power supply (i think you have checked this is OK). The CPU. The analogue stuff.... check through in that order.
    The CPU, see if reset is high (p40). external clock is going (p37). When you push the diag button the PIA ports connected to the DAC 1408 should begin to pulse. In game play mode the PIA ports going to the DAC should also go active when you trigger sounds.
    Introduce noise through the amplifier to check to see if it is likely working. Just twizzling the pot if you get some cracks, pops, and hum is a pretty good sign. When the sound board is connected to the speech card the analogue sound first goes across the ribbon to mix in with speech and goes through the 1458 op amps then back across the ribbon again. A bad 1458 can produce no sound or speech.
    Common issues... I see and AMI brand CPU chip in a possible scanbe socket. So you have an unreliable chip in an unreliable IC socket... double whammy.
    The ribbon cable gets screwed up from the tight bends. It looks like you have the type you can attempt to press down a new ribbon into... last resort to do that... make sure you are sure the ribbon is broken before trying because it does not always end well.
    Not uncommon for the 1458 op amps on the speech board to be blown.

    B & I, That is a lot of great info, I think I read it slow 4 times and likely only got 70%. But I think you want me to look only at Sound board(not card) and break it down into it's 3 functions, then eliminate areas that appear to work(ie: power section.) The remaining 2 sections CPU and analog stuff don't jump out at me. There are a number of IC chips with 9 and 10 being the biggest and both look like 40 pins a piece, but that about it for my identification skills.

    Let me share my latest, since I began to doubt if the 2nd sound board installed was still 100%. I went to a 3rd Sound board from a definitively working machine, my Black Knight. Right or wrong, I figured it was safe as it is same part # w different Roms and I just want to hear anything. Well, you've guessed it, nothing again. For all 3 boards installed I did press the lil test button and got more of the nada.

    I know that my greenhorn experience level is way down in the cheap seats compared to you helpful 3, but I'm having a hard time buying it's a board issue. I know there are limited components left beyond the board down in cabinet, which seem easier/quicker to test. The original speaker did measure open, so I think it's bad. I do have an alternate 8ohm(measured 7.3) speaker alligator clipped in the cabinet with good continuity to board. The other component is the volume control, not sure how to test, but does have continuity back to sound board. I know this may be a folly to check off board, but 2 working boards installed is really messing with me.

    Thanks for letting me express my frustration. I know it's difficult on your side fer sure and ultimately 4 heads are better than my one!

    #14 3 months ago
    Quoted from lpnsocal:

    Incorrect, No Sound Boards work. Originally an alternate FP sound board from a working(prior to going into storage)game placed into project machine, along with other boards as I move along in diagnosis of game issues. Once I saw I had power board issues, I swapped for another in order to continue tests, so I could order all needed parts from Ed in one try. With the alt power board in, game plays etc..but no sound at all. No speaker buzz, nada.

    Ed, I think you are saying that if I had something more than a MM and logic probe I might be able to work backwards on the sound board(not card) and find where the signal ends, Correct?

    B & I, That is a lot of great info, I think I read it slow 4 times and likely only got 70%. But I think you want me to look only at Sound board(not card) and break it down into it's 3 functions, then eliminate areas that appear to work(ie: power section.) The remaining 2 sections CPU and analog stuff don't jump out at me. There are a number of IC chips with 9 and 10 being the biggest and both look like 40 pins a piece, but that about it for my identification skills.
    Let me share my latest, since I began to doubt if the 2nd sound board installed was still 100%. I went to a 3rd Sound board from a definitively working machine, my Black Knight. Right or wrong, I figured it was safe as it is same part # w different Roms and I just want to hear anything. Well, you've guessed it, nothing again. For all 3 boards installed I did press the lil test button and got more of the nada.
    I know that my greenhorn experience level is way down in the cheap seats compared to you helpful 3, but I'm having a hard time buying it's a board issue. I know there are limited components left beyond the board down in cabinet, which seem easier/quicker to test. The original speaker did measure open, so I think it's bad. I do have an alternate 8ohm(measured 7.3) speaker alligator clipped in the cabinet with good continuity to board. The other component is the volume control, not sure how to test, but does have continuity back to sound board. I know this may be a folly to check off board, but 2 working boards installed is really messing with me.
    Thanks for letting me express my frustration. I know it's difficult on your side fer sure and ultimately 4 heads are better than my one!

    For a rudimentary test you don't have to change the sound ROMs... it will work just wrong sound. Maybe since you swapped chips around put the once working board back into the working game to verify that board is still OK just for sanity check.

    For the volume put make sure is not adjusted all the way down or has an open wiper pin.

    The two outside legs of the volume pot should show the full resistance rating (i forget what it is, like 10K or so I imagine). The middle pin is the wiper that adjust. The middle pin to the outside pins should show changing resistance as you twizzle the pot.

    #15 3 months ago
    Quoted from barakandl:

    For a rudimentary test you don't have to change the sound ROMs... it will work just wrong sound. Maybe since you swapped chips around put the once working board back into the working game to verify that board is still OK just for sanity check.
    For the volume put make sure is not adjusted all the way down or has an open wiper pin.
    The two outside legs of the volume pot should show the full resistance rating (i forget what it is, like 10K or so I imagine). The middle pin is the wiper that adjust. The middle pin to the outside pins should show changing resistance as you twizzle the pot.

    Excellent info on checking a potentiometer/ volume control! When I checked it per instruction, I got some odd readings. Never having checked one of those before I checked my BK's volume control and it measures more in line with how results from video should have been albeit for a 5K version. So I cut it out of BK and clipped it into FP and was oddly satisfied with FP wanting to do battle with me!

    So I threw in the original sound FP board and fired it up. There it was, the sound of silence But at least I know the only issue(s) are left on the board. I think there are some write ups that have recommended upgrades to this board, plus some of the usual suspects mentioned by you. My hope since I have limited diagnosis equipment, is to do a rebuild on the board with recommended replacements/sockets/upgrades/etc. Then......I should have a working board! Finding the failed component is important, but replacing it without the remaining weak links seems silly. So, I'll replace them all as they are reasonably affordable. Remember, I'm already going to do the power board.

    With that all being said, If you(or anyone) have a list of recommended components to replace and/or direction to a preferred informational link, please share.

    Thanks again, she's getting closer!

    #16 3 months ago

    You need to swap the two plugs: sound volume and black wires(speaker). Your picture shows them reversed.

    243B06BD-22CC-4645-9981-A383F8AA0D72 (resized).jpeg

    afpk (resized).jpg

    #17 3 months ago

    Ding, Ding, Ding..........We have a winner!!!!!

    I swapped them and it worked..., original sound board now works!!!! Start with the simple stuff someone once said. I sure felt like a bonehead until I checked the backbox photo I take before I start pulling boards, connectors were reversed at that time. Which explains why no sound after I put a working power board in. To be honest.....I am not above reversing connectors, I have just been doing it with way less frequency since taking the "before" pic.

    That was a great catch Pindel it was right there in the posted pic! I'm Super Duper stoked! I can complete my parts list and order.

    Thanks for all the help, tutelage, information, and patience from everyone!

    #18 3 months ago

    Great to hear! I can honestly say i couldn't hold a candle to most of the help here. I bought a storage unit years ago including tons of system 3-7 mpu and sound boards. Since I had zero electronics knowledge they sat for years. When I needed system 6 and 7 boards I dug them out. The cool thing was since I had so many, I was able to do the swap everything out (roms, chips, transistors) trick until something worked. Slowly, I mean slowly, It started to click. I bought some of siegecraft electronics(Hans is the man!) tester stuff, desoldering iron, and finally a probe. I managed to repair almost all the boards that looked totally nasty. I learned a ton and have not found a firepower I couldn't fix. I can basically walk the most clueless person through a repair over the phone. I actually enjoy board problem solving now but can only take it in doses. Glad your good to go!

    asieg (resized).jpg
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