Troubleshooting Zoom H4

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FireAlarmPoet
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Re: Troubleshooting Zoom H4

Post by FireAlarmPoet » Mon Jul 17, 2017 3:32 pm

As I said I already updated the firmware and the issue persists regardless if it's a line out or phone out.

Compare the following:

Recording line out from dual deck (6/25/17) - no problem:
http://vocaroo.com/i/s0UGIVNjONzC
Recording line out from dual deck (7/17/17) - same setup, same tape, different sound:
http://vocaroo.com/i/s1v7QQgImn87

Notice the absence of any tape hiss in the second sample, as if it reads the hiss as pure silence.

Screenshots of the above samples, with the 'normal' clip on top and 'bad' clip on bottom:
Picture 2.png
Picture 2.png (157.6 KiB) Viewed 610 times
So it's not really a DC offset problem per se, more like only some of the waveform is captured.
Picture 3.png
Picture 3.png (158.21 KiB) Viewed 610 times
Close-up.

Something is definitely not right here: I went to record something as an example and I found the built-in mic picking up a signal even though it's set to input 1+2 mode.
Thankfully I was able to record this phenomenon. You'll hear me breathing three times into the mic while set to input 1+2 mode, then three more breaths into the mic while set to mic mode for comparison.
If you listen closely, you can hear a different kind of background hiss between the first three and last three breaths:

http://vocaroo.com/i/s1sOJx0TVhF2

In addition to these anomalies, I debunked the weird room issue. To elaborate, when I was trying to record recently, the Zoom would shut off on it's own if I moved it to a certain place(s) and stay off until I put it in a "sweet spot." This only happened when connected to wall power, it wouldn't shut off on it's own with batteries. I initially thought this was due to my tape deck/cd setup since I had the occasional odd ground hum issue with the 'old' tape deck (everything recorded for the sake of this topic is the 'new' deck). However, I had the same issue of it turning off of it's own accord when trying to record from my noise setup.

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xdugef
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Re: Troubleshooting Zoom H4

Post by xdugef » Mon Jul 17, 2017 3:38 pm

Also I'm not sure but if you take the batteries out and don't give it power it should forget whatever settings you were using and go back to defaults.
FireAlarmPoet wrote:
Mon Jul 17, 2017 3:32 pm
Something is definitely not right here: I went to record something as an example and I found the built-in mic picking up a signal even though it's set to input 1+2 mode.
Okay that is weird.. have you ever dropped it?
FireAlarmPoet wrote:
Mon Jul 17, 2017 3:32 pm
To elaborate, when I was trying to record recently, the Zoom would shut off on it's own if I moved it to a certain place(s) and stay off until I put it in a "sweet spot." This only happened when connected to wall power, it wouldn't shut off on it's own with batteries.
I think at this point you should consider taking it apart and putting it back together. I'm pretty sure I had reassemble mine a couple times after cleaning the battery contacts before everything was seated corrected.. there's a couple of boards that are connected from what I recall.

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Re: Troubleshooting Zoom H4

Post by FireAlarmPoet » Mon Jul 17, 2017 3:53 pm

xdugef wrote:
Mon Jul 17, 2017 3:38 pm
Also I'm not sure but if you take the batteries out and don't give it power it should forget whatever settings you were using and go back to defaults.
Nope, it saves your settings from all the times I've used it. Plus there's no factory reset even with the firmware update. Woo-Hoo!

This is looking more and more like an open 'er up kind of job... that or a suck it in and drop a few hundered on a newer, better recorder kind of job. Will update should I discover anything else relevant, but please keep your suggestions coming in, it really does help.

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Re: Troubleshooting Zoom H4

Post by crochambeau » Mon Jul 17, 2017 4:04 pm

The malformed recordings, how were the tapes transferred to the H4? Tape machine's headphone output to H4 1/4" input?

If you play the tape in your stereo, and record with on board microphones at the H4, do the malformations not occur?

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Re: Troubleshooting Zoom H4

Post by FireAlarmPoet » Mon Jul 17, 2017 4:40 pm

crochambeau wrote:
Mon Jul 17, 2017 4:04 pm
The malformed recordings, how were the tapes transferred to the H4? Tape machine's headphone output to H4 1/4" input?

If you play the tape in your stereo, and record with on board microphones at the H4, do the malformations not occur?
Yes I said before, the sample was taken from the headphone out of the tape deck.
On board microphones sound normal, they are not effected at all. It's like only the input portion isn't working, except that wouldn't explain why input mode is picking up mic signals.

I opened it up and re-set all the PCBs. Didn't notice anything obvious (corrosion, exploded caps, etc). Did this twice and both times it didn't get any better.

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Re: Troubleshooting Zoom H4

Post by crochambeau » Mon Jul 17, 2017 6:18 pm

Do you own a multimeter? I'm guessing your headphone amplifier on the tape machine is fucked.

Can you try an RCA line out to test?

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Re: Troubleshooting Zoom H4

Post by FireAlarmPoet » Mon Jul 17, 2017 6:40 pm

As I said, I tried RCA line out; it doesn't matter if it's line out, phone, aux; cd player, tape deck, cable, mixer, it's all the same result. The only constant factor is the Zoom itself.

This is more and more looking like a future investment in the H4N or something comparable. I mean I could hillbilly hack it to where I disconnect the onboard mics and run leads from the inputa to where the mics once connected on the board, but that's honestly all I can think of and it's a lot of fucking around.

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Re: Troubleshooting Zoom H4

Post by timdrage » Tue Jul 18, 2017 2:12 am

timdrage wrote:
Mon Jul 17, 2017 2:32 am
Some of these recorders have 1/4" inputs which are actually mic level not line level! So it will kind of work but be prone to weird distortion even with the digital level turned down and not apparently clippiblng.. and / or impedance issues

So it might be something to do with that
- fixed weird autocorrects, 'limited be?!

But yeah sounds like something is actually wrong. H4N is great in my experience if you are upgrading

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Re: Troubleshooting Zoom H4

Post by crochambeau » Tue Jul 18, 2017 6:19 am

Do you have phantom power turned on at the H4? That could be pumping a DC offset into the preceding stage that has fucked everything you've tried.
FireAlarmPoet wrote:
Mon Jul 17, 2017 6:40 pm
As I said
Apologies, yeah, my scanning comprehension skills are less than 100% accurate. I may have scanned over you ruling out phantom power as well.

Best of luck!

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xdugef
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Re: Troubleshooting Zoom H4

Post by xdugef » Tue Jul 18, 2017 6:54 am

crochambeau wrote:
Tue Jul 18, 2017 6:19 am
Do you have phantom power turned on at the H4? That could be pumping a DC offset into the preceding stage that has fucked everything you've tried.
I think you have to use 3 wire XLR cables for this to be a legitimate concern

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Re: Troubleshooting Zoom H4

Post by crochambeau » Tue Jul 18, 2017 8:38 am

xdugef wrote:
Tue Jul 18, 2017 6:54 am
crochambeau wrote:
Tue Jul 18, 2017 6:19 am
Do you have phantom power turned on at the H4? That could be pumping a DC offset into the preceding stage that has fucked everything you've tried.
I think you have to use 3 wire XLR cables for this to be a legitimate concern
Phantom works by powering both signal pins of an XLR to achieve a common mode reject-able DC supply with reference to ground.

Those are combo connectors, so the XLR and 1/4" aspect are interleaved at the connector. My H4 has been a piece of shit for over a year, or I'd test it directly, but I don't think it too outlandish to think that maybe there's a little DC on the input jack.

I might be wrong. If FAP has a multimeter, or just menu dives to confirm this is not the state, it'll be resolved as either poppycock or other.

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Re: Troubleshooting Zoom H4

Post by crochambeau » Tue Jul 18, 2017 9:14 am

Okay, because I'm an asshole I just tore my H4 apart, cleaned & reseated the dodgy switches & connectors and put it back together.

Hey it works!

Xdugef is correct in stating that the phantom power should not be reaching the 1/4" connector when engaged. That said, depending on the history of abuse your particular unit has seen, it's not outside the realm of possibility something has been tweaked out of joint.

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Re: Troubleshooting Zoom H4

Post by xdugef » Tue Jul 18, 2017 9:26 am

crochambeau wrote:
Tue Jul 18, 2017 9:14 am
Xdugef is correct in stating that the phantom power should not be reaching the 1/4" connector when engaged. That said, depending on the history of abuse your particular unit has seen, it's not outside the realm of possibility something has been tweaked out of joint.
There's certainly no harm in making sure phantom is turned off.. but after Chris further explained what was going on I don't think it's DC offset anymore. I don't think it's a problem with the jacks because it's unlikely both would go south at once so it's either the preamp or some other multipin connector inside it. Anyway.. time to upgrade.. the H4 is kind of a POS in comparison to newer models.

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Re: Troubleshooting Zoom H4

Post by crochambeau » Tue Jul 18, 2017 10:55 am

xdugef wrote:
Tue Jul 18, 2017 9:26 am
some other multipin connector inside it.
Yeah, the bottom input block PCB connects with a single connector, exercising that may be of benefit. I want to say I was able to work that cluster without digging into the front shell (watch for flying switch caps) - but since I did go all in on it I can't recall for sure. It was a fast and dirty rip down and rebuild, and I was not taking time for notes.

If it's an electronic failure I'd expect it to be a little more nefarius, since the same circuit that handles the positive excursion of your signal is supposed to handle the negative excursion as well, and since it's doing the one you're not looking for DOA stuff which is inherently easier to spot. Maybe there's a negative rail charge pump that's kaput? Floating common reference? DC tickling the ground plane on the input connection block (sorry, couldn't resist).

I'm sure the newer stuff is nicer, but for a paid for device if it can be made to work with a little effort it's worth having even if you do upgrade and it just becomes something you tape to the inside of your engine compartment while driving around town.

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Re: Troubleshooting Zoom H4

Post by FireAlarmPoet » Tue Jul 18, 2017 3:58 pm

crochambeau wrote:
Tue Jul 18, 2017 9:14 am
Okay, because I'm an asshole I just tore my H4 apart, cleaned & reseated the dodgy switches & connectors and put it back together.
Hahaha, I'm not going to lie, I was kind of hoping to goad you into looking at your own H4 and come up with a solid fix.
I may still do another tear-down/reseating to see if there's anything I missed (I didn't check out the PCB where the screen is kept under) and that may yield success, but as you said, even if I can get it to work again I think the writing's on the wall.
By the way, I was kind of shocked at how flimsy all the PCBs fit together. No standoffs or anything. Is this common? That once board that bridged the inputs with a board perpendicular to it was only held up by that connector in the middle; that to me is analogous to a jenga tower held up on the very bottom by just one block in the middle.

Also, if I recall correctly, toggling phantom power did nothing. I'd agree that it's possible it could've messed up the inputs somehow, but still an easy fix there is not.

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