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Need help on pair of pioneer gm-h120's
Need help on pair of pioneer gm-h120's
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Old 22nd January 2019, 10:32 AM   #21
Perry Babin is offline Perry Babin  United States
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Did you check the shields?
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Old 22nd January 2019, 11:02 AM   #22
1930essex is offline 1930essex  Canada
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Ill give it a try when i get home tonight however
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Old 22nd January 2019, 11:03 AM   #23
Perry Babin is offline Perry Babin  United States
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Is the head unit being powered from the same power supply as the amp?
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Old 22nd January 2019, 11:06 PM   #24
1930essex is offline 1930essex  Canada
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Perry no i use two separate power supplys....i grounded the sheild to the ground lug on the amp and it works perfectly...my hat off to you! You are a vast wealth of knowledge sir! I thank you very much! I have learned quite a bit from just this little problem you have guided me through!
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Old 23rd January 2019, 01:02 AM   #25
Perry Babin is offline Perry Babin  United States
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Now, the GM-H100 should also work.

Connect the grounds of the two supplies with a jumper wire to prevent this in the future.
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Old 23rd January 2019, 02:41 AM   #26
redrooster is offline redrooster  Australia
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Yay! Mystery solved! Good on you Perry!
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Old 23rd January 2019, 11:19 AM   #27
1930essex is offline 1930essex  Canada
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Yes thanks again perry....are these pioneers the only amps that are designed this way or is there other ones out there? Like I mentioned ive got over 30 amps all different brands that i have tested with this same setup and they all work like they should....
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Old 23rd January 2019, 01:12 PM   #28
Perry Babin is offline Perry Babin  United States
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I don't know what you mean by 'these pioneers'. There are multiple models of Pioneer amps that have this problem. Some Alpine amps have various problems. I've seen other amps that had various problems with floating shields. It generally shows up when people try to use their phones/MP3 players (which don't have a connection to the vehicle ground).
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Old 23rd January 2019, 10:58 PM   #29
1930essex is offline 1930essex  Canada
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By these pioneers i mean the gm-h series
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Old 27th January 2019, 04:27 PM   #30
tulowd is offline tulowd  Canada
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GMH Series high current amps have the old idiotic dual turn on system; I can't tell by the previous posts whether this has been adequately addressed and explained. The floating inputs on the Pioneers are a design to prevent in car noise and in my considerable experience, worked exceptionally well as the 6 years I ran their car audio tech department for all of Canada, noise questions basically did not exist.......unlike many other amp brands from back then, lol

The main B+ and B- terminals get the 8 or 10g power and 18" ground leads.

The 2 pin connector with the blue and red wires (lower right side of amp below RCAs in the pic) needs +12V on the red wire (supposed to come from the accessory circuit) and the blue gets the usual remote turn on from the head or eq etc.) I remember begging and arguing during product planning in 1990 to get rid of this needless additional circuit, but they insisted.

If you give the red wire constant current, it will drain the battery; the blue circuit from the radio will not have enough current to latch the relay on the red circuit; as it needs about 1 amp at 12V IIRC.

Hoping this helps you, cause in my mind, there's no way three of those old beasts are experiencing a strange failure like this collectively. I still have a GMH120 from 1992 that has had the daylights kicked out of it and still works as well as the day it was new.
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Last edited by tulowd; 27th January 2019 at 04:30 PM.
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