http://www.hafler.com/techsupport/pdf/DH-500_amp_man.pdf
Hi, what is written on the relay ? It seems an unusual (right current rating,chassis mount, large) one for this purpose. Good ! You can use another 48 V relay with contacts for 12 A or better 16 A. Other relays can be used if you add a small transformer with the right voltage. Use relays with "hard silver" contacts.
Being used to replacing 2 A rated relays in japanese power amps I replace those with Schrack/TE RT2 type relays. They have 8 A contacts and never failed on me till now. I wish they made 16 A double pole relays but they don't in this format. You can use the single pole RT1 version which is rated 16 A but you will need 2 of those. I have a hunch that you can use the coils of 2 x RT1 48 V rated relays in series if you change R120 to 0 Ohm but please measure power supply voltage that is over the coil of the old relay first....and check again if you choose this way after you added 2 relays and measure per coil.
Of course you will need to put a diode in reverse parallel of the coils (one diode per relay coil) to avoid reverse high voltage.
Hi, what is written on the relay ? It seems an unusual (right current rating,chassis mount, large) one for this purpose. Good ! You can use another 48 V relay with contacts for 12 A or better 16 A. Other relays can be used if you add a small transformer with the right voltage. Use relays with "hard silver" contacts.
Being used to replacing 2 A rated relays in japanese power amps I replace those with Schrack/TE RT2 type relays. They have 8 A contacts and never failed on me till now. I wish they made 16 A double pole relays but they don't in this format. You can use the single pole RT1 version which is rated 16 A but you will need 2 of those. I have a hunch that you can use the coils of 2 x RT1 48 V rated relays in series if you change R120 to 0 Ohm but please measure power supply voltage that is over the coil of the old relay first....and check again if you choose this way after you added 2 relays and measure per coil.
Of course you will need to put a diode in reverse parallel of the coils (one diode per relay coil) to avoid reverse high voltage.
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The existing relay Coil is open - and the amp never gets out of standby - I temporarily removed the relay and jumpered the speaker outs - works perfect with no relay, with a little turn on thump. No issues with DC Offset (within 15mv)
Kinda tempted to leave out the relay - as I said, works perfect, with a small turn on thump (I have heard much worse).
Here is what relay says (may not be original)
Magnecraft
388CQX-14
48VDC
12A @ 120VAC/28VDC
12A @240VAC UL
10A @240VAC CSA
1/3HP @ 120VAC
1/2HP @ 240VAC
Kinda tempted to leave out the relay - as I said, works perfect, with a small turn on thump (I have heard much worse).
Here is what relay says (may not be original)
Magnecraft
388CQX-14
48VDC
12A @ 120VAC/28VDC
12A @240VAC UL
10A @240VAC CSA
1/3HP @ 120VAC
1/2HP @ 240VAC
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Hi I left relays out in some cases many years ago but equipment does fail sometimes and then it will be your speakers that will hate this decision....they will forgive you for the few hundred power on thumps.
There is hope:
http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=388CQX-3
http://www.weisd.com/store2/NTER10-5D10-24F.pdf
There is hope:
http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=388CQX-3
http://www.weisd.com/store2/NTER10-5D10-24F.pdf
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Just saw it when you replied. Then the Schrack relays are an option. I possibly have some in stock but I doubt shipping costs will make it a good deal for you. Better find panel/chassis mount 48 V relays in the US. Like this one:
http://download.siliconexpert.com/p...l/eng_ds_kuep_series_relay_datasheet_0910.pdf
http://www.arrow.com/item/detail/te-connectivity/8-1393113-8
http://download.siliconexpert.com/p...l/eng_ds_kuep_series_relay_datasheet_0910.pdf
http://www.arrow.com/item/detail/te-connectivity/8-1393113-8
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It's a control voltage, change the circuit so that it does the required voltage - and actually relays don't care much about voltage, as long as you don't overdo it by a lot. I seem to recall altering the circuit so that I could use a 24vdc or 12vdc, don't remember which to power the relay. An LM317 might do the trick too, haven't looked at the schematic... I suggest a 4PDT relay, use paralleled contacts. I think that they sound better.
_-_-bear
_-_-bear
Simplest would be to choose the right voltage straight away especially when they are available and one needs to order one anyway.
Using a relay rated for lower coil voltages will result in the need for a power dissipating circuit which won't be as reliable as a simple relay coil. Loss of power, conversion to useless heat, more parts. Something of the past.
Paralleling the contacts is OK but one of them will be slightly faster than the other which is why it is not done often in power circuits. There are special relays out there that have different contact materials for this purpose. The contacts that close first are purely for current switching and the second contacts are better conducting materials that do not like high current switching.
http://www.europe-audio.com/Product.asp?Product_ID=4469
Using a relay rated for lower coil voltages will result in the need for a power dissipating circuit which won't be as reliable as a simple relay coil. Loss of power, conversion to useless heat, more parts. Something of the past.
Paralleling the contacts is OK but one of them will be slightly faster than the other which is why it is not done often in power circuits. There are special relays out there that have different contact materials for this purpose. The contacts that close first are purely for current switching and the second contacts are better conducting materials that do not like high current switching.
http://www.europe-audio.com/Product.asp?Product_ID=4469
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jean-paul, what you say is true, but...
this relay is in the speaker line and closes before there is any signal running through the amp, unless you happen to have left the volume up and the CD player running when you turn it on...
also even if one contact closes first and takes the 'heat', the second contact doesn't and improves the connection.
in this case if the capabilities of the original contacts are doubled in the 4PDT relay, so the contact resistance is reduced substantially, especially in the case where there has been any degradation...
I did not suggest running a 24v relay on 48v, although a bit more heat is really not a big deal in an amp that is several hundred watts output per channel, what I was aiming at and suggested is reducing the rail voltage for this control circuit...
...having worked on a number of these Hafler amps it's my suggestion that a number of basic mods will result in a better sounding amp:
- improve the ground connection between the filter caps
- upgrade the ground and B+ wiring, wiring to the speaker outs
- better rectifier bridge
- multiple relay contacts per channel (using two relays is a possiblity)
YMMV.
_-_-bear
this relay is in the speaker line and closes before there is any signal running through the amp, unless you happen to have left the volume up and the CD player running when you turn it on...
also even if one contact closes first and takes the 'heat', the second contact doesn't and improves the connection.
in this case if the capabilities of the original contacts are doubled in the 4PDT relay, so the contact resistance is reduced substantially, especially in the case where there has been any degradation...
I did not suggest running a 24v relay on 48v, although a bit more heat is really not a big deal in an amp that is several hundred watts output per channel, what I was aiming at and suggested is reducing the rail voltage for this control circuit...
...having worked on a number of these Hafler amps it's my suggestion that a number of basic mods will result in a better sounding amp:
- improve the ground connection between the filter caps
- upgrade the ground and B+ wiring, wiring to the speaker outs
- better rectifier bridge
- multiple relay contacts per channel (using two relays is a possiblity)
YMMV.
_-_-bear
I would not doubt the possibility of the wrong one was in there...
Or did I just get the coils and relay backwards??
HAFLER DH500 RELAY -- ORIGINAL PART | eBay
Or did I just get the coils and relay backwards??
HAFLER DH500 RELAY -- ORIGINAL PART | eBay
This is also possible when a replacement relay can not be found:
Velleman nv - Item - Details
I would never bother with MOSFET switching and keep it simple. Better find a suitable chassis/panel mount relay with silver contacts. Just suppose you don't hear the "click" anymore at power on
Velleman nv - Item - Details
I would never bother with MOSFET switching and keep it simple. Better find a suitable chassis/panel mount relay with silver contacts. Just suppose you don't hear the "click" anymore at power on
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The relay is for protection of your speakers in case of catastrophic power transistor failure/loose wiring i.e. any reason that causes full rail voltage at the output. Second function is to avoid power on "thump".
The first function is somewhat more important. In my limited experience quite a few amps that were without protection relay took the speakers with them when they failed. Expensive, not nice, unnecessary. You can protect your valuable speakers for a few dollars.
The first function is somewhat more important. In my limited experience quite a few amps that were without protection relay took the speakers with them when they failed. Expensive, not nice, unnecessary. You can protect your valuable speakers for a few dollars.
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Imho, this is being made too difficult.
First any (coil) voltage relay can be used by one of two means:
- increase the power rating of the series transistor (Q101) by replacing it with a higher current device *and* changing the series resistor R120for a higher wattage and larger value (for more voltage drop). You want to end up with slightly more voltage available for the new coil than it is nominally rated at. So, if you put in a 24vdc unit, you'd want to hit it with say 28vdc - the key is that the relay must pull in decisively.
- put a suitably sized 3 pin voltage regulator in the B+ line going to the regulator. The place for it is after the simple 1/2 wave rectifier D105. Here you have to be careful about the power being dropped by the vreg... so it might be necessary to put a resistive divider in place first... yeah it wastes heat, so what. Not much.
Now you can choose between many different relays, or do as I did, use two relays mounted side by side, with multiple paralleled contacts.
First any (coil) voltage relay can be used by one of two means:
- increase the power rating of the series transistor (Q101) by replacing it with a higher current device *and* changing the series resistor R120for a higher wattage and larger value (for more voltage drop). You want to end up with slightly more voltage available for the new coil than it is nominally rated at. So, if you put in a 24vdc unit, you'd want to hit it with say 28vdc - the key is that the relay must pull in decisively.
- put a suitably sized 3 pin voltage regulator in the B+ line going to the regulator. The place for it is after the simple 1/2 wave rectifier D105. Here you have to be careful about the power being dropped by the vreg... so it might be necessary to put a resistive divider in place first... yeah it wastes heat, so what. Not much.
Now you can choose between many different relays, or do as I did, use two relays mounted side by side, with multiple paralleled contacts.
Yes, considering the DH-500 speaker outs already have fuses, and none of my other amps have such protection...hmmmm....I will just put the correct relay in. I don't think it will be dethroning any amps I have (sounds very good, but I prefer my other amps), so might just as well fix it up right...
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