2220B Troubleshooting

Discussion in 'Marantz Audio' started by mvh363, Jul 10, 2018.

  1. mvh363

    mvh363 New Member

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    I have recently purchased a Marantz 2220B as-is, fully expecting it wouldn’t be fully operational. I’ve done some basic service on amplifiers before so I figured it wouldn’t be too difficult a task to try and get this one going, but my limited knowledge and experience has unfortunately left me stumped on the most significant issue.

    I cleaned it up so I could visually inspect for any obvious component failures, hooked up some sacrificial speakers, and powered it up. I found the right channel operates as-expected, but the left channel produces a loud crackling that is completely unaffected by the controls - changing the input, or adjusting the volume and balance does nothing to affect this noise, but the audio underneath is still present. Since it’s only affecting one channel, it seems logical that the fault isn’t in the power supply, and as it’s unaffected by controls, led me to believe the fault is in the power amplifier.

    Initially, I thought it might be an issue with the output transistors, but I pulled and tested them with a multimeter and they seemed fine. I then checked the bias on the outputs using the locations posted in the service manual correction thread, and both channels were out of spec, with the left moreso. I adjusted the right, but the left channel wasn't giving me solid readings while trying to dial it in, so I’ve put that off for now assuming that the bias issue in that channel are largely another symptom of the primary fault I've yet to ascertain.

    Any ideas what I should be focusing on at this point? I thought it may be an issue of bad capacitors due to the unit's age, so I ordered the requisite components for a recap, but I don’t know if they would cause this sort of issue without any immediately noticeable signs of failure on the main amplifier board.
     

     

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  2. Jailtime

    Jailtime Standin' on a corner Subscriber

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    Seems to me like you have narrowed it down pretty well. Take a look at the differential pair transistors, H701 thru 704. Gain match them in pairs with a multimeter that has hFE function. KSA992 would be a good replacement for them.
     
  3. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

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    Don't discount the age of the Receiver. I rebuilt a Marantz 1060 recently with the same sort of symptoms - replacing the capacitors on the amplifier board solve the problem - Chris
     
  4. buttahman

    buttahman Active Member

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  5. mvh363

    mvh363 New Member

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    Thanks for the help everyone, I really appreciate it and my amplifier is coming together nicely.

    Now I need to handle the other minor issues, but I think I've got those figured out. There's a handful of bad caps on the MPX board which explains the lack of Stereo over FM, but the signal meter is stuck and doesn't seem to work on AM either and I don't know if the MPX board would have anything to do with that, or if the meter is simply shot. I'll also have to replace/upgrade the fuse lamps since half of them are out, but that should be relatively easy in comparison.
    I was waiting for the transistors to come in before I bothered to recap the power amplifier because it's less than accessible. I swapped the differential pairs with matching sets while changing out the caps and now it's dead silent at idle, so thanks for the tip.
    The leads on the transistors didn't look so great after I got a better look at them, so they were probably the issue.
    Who would have thought that the freebie multimeter from Harbor Freight would have be the MVP for this project? I'm surprised it was the only meter I had with an hFE function.
     
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  6. mvh363

    mvh363 New Member

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    I finally got around to swapping the rest of the caps in the unit, which were all related to the AM and FM capabilities of the unit. Even though I'm not really in need of a working tuner, it didn't feel right to leave it sit with multiple leaking caps where things could get worse should I ever change my mind.
    The tuner is now much more usable than it was prior, but I've still got some issues with it and I want to make sure it's not just misalignment, so if this is better suited for the tuner subforum I apologize.

    For a quick rundown of symptoms:
    The signal meter still doesn't move while adjusting tuning, nor do I have stereo on FM (no light, or stereo audio from what I can tell in very informal testing), but the meter does move ever so slightly from the center rest position when switching to and from FM and AM, but otherwise remains stationary. Moving the tuner around in either mode doesn't seem to affect the voltage across the meter either.
    With AM selected, output is dead silent at all levels and frequencies, and I unfortunately don't recall if performed the same way prior. I checked for a signal at H104 Pin 11 as per the service manual and I didn't observe any voltages - seeing as I get no audio output this makes sense, but I'm a bit worried that I'm seeing nothing at all from the chip.
    As for the FM output, it behaves in an unusual way. When a station is centered on the dial, the output is strong but obscured by distortion. If you tune beyond a station, it comes in basically crystal clear but the output is at much lower levels. Elsewhere on the dial, you get white noise as is expected of an analog tuner.


    As mentioned earlier, I naturally would assume the tuner is out of alignment since I had replaced multiple components on it, but I'd like to make sure there's nothing else that might be going on since tuners are well out of my wheelhouse.
     

     

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  7. rBuckner

    rBuckner Luv 2 Restore Subscriber

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    For a starting point, have you checked the power supply voltage at the tuner boards? Wires can get pinched and take years to finally have a break in the insulation that shorts the wire to chassis ground. So look around for those too.

    Put that meter in resistance mode and put the leads onto the meter contacts briefly. the needle should jump one way or the other depending on the polarity of the leads. I'm thinking the negative side is to the right viewing from the front of the stereo and probably has a black colored wire. It will be the one that has a jumper wire to the other meter.
     
  8. mvh363

    mvh363 New Member

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    The Power Supply voltages are all looking good to me on the tuner boards.
    Also the signal meter does jump when testing resistance, so it does appear to be functional. Unfortunately, the problem is not the wiring connecting it, as there's no resistance across the lines and J104 tests at 0V. I see that the meter is dictated by pin 14 of H104 in AM, and it's sitting at 0V. I'm still trying to work it out on the FM side, but I figured I'd update first.
    I did some more poking around at H104 in regards to whatever is happening with the lack of any AM reception. They seem to test fine, but pins 2-4 are 12.84V instead of 13.1V, pin 8 is 8.43V instead of 8.9, and 10V is 12.94V instead of 13.3V, but that should be within tolerances. Also, when rechecking pin 11, it measures 1.5VDC, but as mentioned prior I see no AC on it nor off of H105 which is said to amplify the the output of H104. I expected I'd at least see something, but there's not even white noise getting picked up. I'm not sure if this indicates that I should replace it with a new HA1151 or if something else is the cause.

    I don't have an appropriate RF signal generator so I can't formally test anything, but tuning to the strongest FM signal I can find, R312 reads 19.05khz off my multimeter. I don't know how close I actually need to be to 19khz, but I can dial it in if need be.

    The FM issues keep looking more and more like an alignment problem, but AM and the signal meter seem to be more complex.
     
  9. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

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    I don't know your radio but my 2230B is probably pretty close. Yeah, the caps on all the FM boards and the AM board were junk. Several were outright bad and the rest had drifted +50%. Mine has a cap across the meter terminals. I also have an attenuator switch on the back that killed the meter until I gave it a good soak in DeOxit. Sensitivity was down till the muting amp caps and pot were replace/cleaned. Now the stereo light works again as it should and I have pretty good sensitivity. I did give the tuning cap a good scrub with electrical contact cleaner ( auto) not deoxit. When I used dioxit on the tuning cap, it messed with the sensitivity and I had to clean it off. I ended up using just a few drops on the bearing/shaft where the contact take place and left the vanes bare and dry. I also had to give the selector switch a double bath of Deoxit to get it working right. One trick on the selector switches is to use a wooden Q Tip with dioxit and scrub the rings if you can get to them. Oxidation will come off nicely with a bit of scrubbing. But not all switches have the room to get physical with it. ( works really well on old Heathkit gear BTW).
     
  10. mvh363

    mvh363 New Member

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    I figured H104 was faulty given I found a similar issue was resolved in a different amplifier, so I got a replacement for it, and it seems that this had not resolved the issue. At this point in time I'm getting 0V DC on Pin 11 nor any audio signal in AM, so I'm thinking that my initial 0V wasn't a measurement error after all, but I can't figure out what's causing it.

    I replaced all of the electrolytics, but I would assume the ceramics and such are fine.
    The 2220B doesn't have a cap across the meter nor an attenuator switch that I'm aware of, but I do appreciate the idea.
     
  11. mvh363

    mvh363 New Member

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    I hate to bump this after so long, but I had the project shelved for a while and have been enjoying the use of the receiver. I recently managed to resurrect the AM section with some donor parts from a unit in far worse shape and it seems to function as intended. The signal meter appears to work well (though it doesn't always deflect as much as I would expect, I do get full deflection at times so I'm sure it's all in order), and the audio level is good. I'm sure the alignment could use some fine tuning, but for now, it works well enough and everything is where I would expect on the dial.

    I'm still looking to finish up the FM section, and I feel I'm starting to grasp what's going on so I've documented my troubleshooting process. I'd like to make sure I'm looking in the right place.

    To recap the issue: FM audio is still very weak compared to other outputs, often reduced even further when tuned to minimize distortion. In addition to this, FM muting will kill all but the strongest of stations, and even that station may as well be dead at full volume. The signal meter also does not deflect any appreciable degree under FM signals, but very slight movements can be observed from center on a handful of stations on the dial. In addition to this, I don't see stereo audio. Because of these symptoms, I believe the fault may lie with P200 (FM IF), or P300 (FM MPX). I assume P100 is now fine barring some minor alignment issues. For now, I've focused on P200.

    I first wondered if it had something to do with improper AGC, as on one particular station that I would expect to be strong given reception on other tuners, but it's virtually inaudible even at full volume. In this state, H101's gate was low (roughly -1.3VDC). If you tuned that station off of center, the voltage comes up, and it becomes more audible, but still much more quiet than the other inputs. It does not appear to engage with most other stations, and none at anywhere near the same level, so I assume it works appropriately.

    From here, I decided to explore voltages on P200.

    Transistor voltages (as per board label) are as follows:
    H201 - B: 3.3VDC, C: 7.9VDC, E: 2.6VDC
    H202 - B: 3.4VDC, C: 7.6VDC, E: 2.7VDC
    H203 - B: 3.0VDC, C: 9.1VDC, E: 2.3VDC
    H204 - B: 3.2VDC, C: 8.6VDC, E: 2.8VDC
    H205 - B: 1.9VDC, C: 13.5VDC, E: 1.63VDC - These voltages are well out of spec. This is the final IF amplifier before the muting circuit, so a failure here would explain at least one of my problems.
    H206 - B: 3.5VDC, C: 12.2VDC *, E: 2.8VDC - *Lower than expected 13.2 but acceptable.
    H207 - B: 0 VDC, C: 13.9VDC (0VAC)*, E: 0.05VDC (0.350VAC) - Emitter AC low, * on Collector because manual suggests 14.3VDC and 14.3VAC but I assume this is an error, as the rail is not expected to be AC elsewhere on schematic
    H208 - B: 0.04VDC (0 .350VAC), C: 0.16VDC (0.160VAC), E: 0VDC (0VAC)
    H209 - B: 0.01VDC (0.010VAC), C: 7.2VDC (0VAC), E: 0VDC (0VAC)

    I'm thinking that H205 should be replaced? It's a 2SC1047C, what would be the ideal substitute for that?
    Before I do that, however, there is an oddity around H205 in the schematic vs my board that's confused me. R227 is supposed to be 4.7k. Instead, I have a 2.7k resistor at R227 in parallel with R267 (22k), which is not on the parts list or schematic. I was wondering if I should place a 4.7k here, but I feel Marantz's engineers probably knew what they were doing and revised accordingly. I do have the Dolby FM board, so I assume this was a later revision than the service manual.
     

     

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  12. Steven Tate

    Steven Tate AK Subscriber Subscriber

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    Great learning opportunity. Anxious to hear from some experts. Great documentation! :lurk:
     
  13. catrafter

    catrafter Marantz Specialist Subscriber

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    I'm not sure how you ruled out the P100 tuner as the problem.
    I keep a spare known good tuner around and use it as a substitute to find out where the problem lies.
    In many cases I have found the real problem is a broken wire or ground strap near the antenna terminals or at the tuner input.
    If the tuner is weak, the AGC signal from the IF amp feeding the tuner will be weak, making it hard to tell where the problem lies.

    In my experience, on the IF amp schematic, the numbers in parentheses () indicate the expected DC voltage (with respect to chassis ground) when a strong station is tuned in. The numbers NOT in parentheses are with no station tuned in.
    On the MPX board, the numbers in parentheses are with a strong STEREO station tuned in. The numbers NOT in parentheses are with no station tuned in.

    YMMV,
    Tom
     
  14. mvh363

    mvh363 New Member

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    I unfortunately cannot find any "simple" fault of that sort, though it's possible I've missed something.
    I cannot guarantee my issue is not the P100 tuner, but FM exhibited the same symptoms with both tuner boards I had. While neither were confirmed to be "good", I was doubtful they had failed in the same way, but it is possible.
    The only measurement that's really anomalous with P100 is H105 (which I don't believe would have any impact on FM reception), but I'll list them all for good measure.
    H101 - D: 13.2V, S: 0.03V, G: -1.5V to 0.0V (ranges based on tuning)
    H102 - B: 2.3V, C: 12.3V, E: 1.6V
    H103 - B: 6.2V, C: 13.9V, E: 5.5V
    H104 - All pins good when last tested
    H105 - B: 2.6V, C: 6 .7V, E: 2.0V - All voltages are a bit low, but the collector moreso with 8.2V expected. However, it works otherwise.

    I considered poking around with a scope, but I only have access to 10mhz unit so I don't think it'd be of much use for troubleshooting RF/IF issues.
    If the parentheses on the IF board do relate to DC voltage when a signal is "locked", that would explain some things. They resembled the AC measurements I took at those points so I had assumed that was their purpose. Unfortunately, this also means my problem might be greater than I had anticipated. On the plus side, a quick pass of the MPX board also yields good voltages on all the transistors (given "poor" reception):

    I wondered if maybe I weren't getting enough of a signal from P100 since FM volume is very low, but I am unaware of how I should check without a better scope.
     
  15. catrafter

    catrafter Marantz Specialist Subscriber

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    If you have tried two P100 tuners and the symptoms remain the same then I would think that the problem lies elsewhere.

    A 10mHz bandwidth scope should be OK for go/no go troubleshooting of the 10.7MHz IF signal. It will read lower in amplitude than a wider bandwidth scope would, but should still be usable.

    I did notice that the base of H205 reads lower that expected. This voltage is primarily supplied by +13V on J204. With the readings you provided, (H205 B 1.9VDC, E 1.63VDC) the discriminator transistor appears to be biased off.
    Could you be missing the +13VDC at J204?

    A quick test of the discriminator output can be made by connecting an RCA cable from the rear panel 'Quad Out' (quadradial out on some receivers) jack to the left Tape In jack. Select FM and tune in a strong station. Press the tape monitor function to hear the discriminator output in the left speaker. This works on most Marantz receivers, not just the 2220B.

    Tom
     
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  16. mvh363

    mvh363 New Member

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    Thanks for the tip about the discriminator. Given the test you described, the audio is similar to the output level I have now, but a tad quieter (even with the Right speaker disconnected, so it's not an issue of two speakers vs one).
    The only confusing aspect of this is that if the discriminator is good, the center tune meter should work, but it really doesn't do much on FM.
    I've might still thoroughly look it over with the scope but it just occurred to me that a signal induced by a scope probe (or a DMM, actually) at many points is quite a bit louder than a tuned station. Is that normal? There should be some signal amplification on P100 so I'd think any injected signals would be quieter. I was a bit surprised to hear some AM stations through the FM stage.

    I do have 13.88VDC on J204, which is good, but I would've preferred to see a bad wire there if I'm being honest.

    I think I've got it on now if it wasn't before, but it hasn't gotten me any closer to a solution.
    This made realize just how much of a mess Marantz' service manuals are. Everything I'd seen up to this point was a flipped cap here or there. No major differences.
    It's far worse than that. On the small section of P200 around H205 vs the manual, R225 does not exist, nor is it on the parts list, but it's 100k on the schematic. Where it would be is L203 (a 150uH choke coil).
    As mentioned before, R227 is 2.7k on my board, the parts list says 3.3k, and the schematic says 4.7k. It's in parallel with a 22k R267 that's not on the parts list or schematic. R228 is 15K on the parts list, schematic, and board.

    It has been a long time since I'd taken a physics class, but I realized R228 and R227 act as a voltage divider, so this seemed indicative of the issue with H205.
    (Source voltage * R2) / (R1 + R2) = Output Voltage.
    For simplicity's sake, I'll assume the 51ohm R242 is 0ohm to make calculations easier.
    With the board I have, with the 2.7k R227 and 22k R267 in parallel, there is ~2.4k effective resistance. R228 is 15k.
    (13.88V * 2.4k) / (15k + 2.4k) = 1.91V
    I previously measured 1.9VDC on H205's base, so the math looks right.
    So wouldn't the transistor never bias "on" in this arrangement?
    Compared to the schematic.
    (13.88V * 4.7k) / (15k + 4.7k) = 3.3V

    It must have come from the factory like this, but I don't have much to lose, so I decided to pull R227 and R267 and I put a 4.7K in their place, and the voltages appear to make more sense now.
    H205 is B: 3.2VDC, C:13.2VDC, E: 2.7VDC, very close to the schematic.
    No other voltages have changed significantly, saved for reduced effectiveness of the AGC. My FM reception is still terrible (it may be a bit worse), and this did result in a slight shift of the center tune/signal meter to the left. It still does not deflect in any appreciable amount. The detector test yields no different result after the change.

    This could be easily reversed if need be, and given no obvious improvement, I'm wondering if I should be looking at P100 after all.
     

     

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  17. catrafter

    catrafter Marantz Specialist Subscriber

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    If you tried a know good tuner (P100) and the problem remained the same, I would think the problem would be down stream of the tuner.

    You circuit analysis of the base voltage on H205 looks right to me, but may discount the effect of the 10.7Mhz IF signal that should be present along with the DC bias.
    It appears to me that the DC bias would have H205 (an NPN) transistor operating as a class A amplifier, the IF signal would then be amplified linearly.
    I think you are losing the IF signal in the IF amp or it is not coming out of the converter (mixer) in the tuner section for some reason.
    If someone has a 2220B on their bench, maybe they could take some scope and DC voltmeter readings for you.

    Tom
     

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