Power Supply for Rane HC6 Headphone Amp

[dbishopbliss]

While not exactly a tube amp, I'm hoping someone can help me out. I have a Rane HC6 built in the 1980s (I think). Unfortunately, I do not have the power supply. Rane quit making the power supplies back in 2009. Based on their literature, it doesn't seem like it would be that hard to make one. They use an RJ12 connector (6 wires) to supply 9VAC on four of the wires (2 in parallel) and two wires for a center tap. I have a 18V, Center Tapped (9-0-9) transformer, some RJ12 cable, an IEC plug and a project box already.


Here's my question... If I were to connect the primary wires to the IEC plug and connect the secondaries to the RJ12 cable according to their diagram, is there anything else I need to do?  What happens if it was plugged in to the wall but not connected to the headphone amp?  What if it was plugged into the amp, but the amp was off? Does the project box also need a fuse and a power switch?


Thanks for your help.


(meanwhile, parts have started arriving for my AC15 build)

[HotBluePlates]

... If I were to connect the primary wires to the IEC plug and connect the secondaries to the RJ12 cable according to their diagram, is there anything else I need to do?  ...

You will need to look inside the device you're powering to understand if there is a particular phasing required from each pin of each 9vac pair on the RJ-12 plug. That is, if the two 9v pairs really are in parallel (Rane's reference to 18v, 9+9v implies either series or 2 independent halves for a bipolar power supply), you need to be sure to orient phasing properly to avoid cancelling the supplied voltage to zero.

What happens if it was plugged in to the wall but not connected to the headphone amp?

Nothing. What happens when you don't plug anything into an outlet in your wall?

What if it was plugged into the amp, but the amp was off?

Nothing. What happens when your stereo (or guitar amp) is plugged in the wall with the power switch off?

Does the project box also need a fuse and a power switch?

The original supply didn't have a fuse or switch. You can add either or both if they make you feel better. I'd expect 18v @ 1A = 120v @ 150mA, so you need the fuse rated at the closest value to 150mA but over, which doesn't pop every time you turn on the power switch or plug in the supply.

[PRR]

HC6 got up-up-up-up-dated over the decades.

This description seems to match the "1989 schematic":
http://www.rane.com/oldman.html#gpm1_8
http://www.rane.com/pdf/old/hc6sch89.pdf

Page 4, lower, is power supply.

It *is* 18V AC CT, but the connections on the 6-finger connector are a mess. There was probably a reason (obviously ground on outside, but after that I am baffled).

_I_ would look for a NON-audio 3-pin connector, both genders, and nail it in. That mod connector isn't robust enough for decades of gigging. It is also going out of style (when was the last time you wired a hard-wire telephone? With a 6-finger?)

I'd really consider nailing the whole transformer on the outside back. Haywire it first to see if it throws hum into the amplifiers. You probably want to stay away from the Level pots and Z1 booster chip. Ah, I see there isn't much back-panel space to spare. You'll figure something out.

[dbishopbliss]

What if it was plugged into the amp, but the amp was off?

Nothing. What happens when your stereo (or guitar amp) is plugged in the wall with the power switch off?

But the switch is BEFORE the primary of the guitar amp transformer.


The reason I asked, one time I was measuring the unloaded secondaries of an unmarked transformer to determine the voltage and someone told me that if I left the transformer plugged in it would burn up. Sounds like I was told the wrong thing.


Anyway, I wired up everything and plugged it in... works fine. Interesting note in the manual about grounding the unit (thanks for the link, not sure why I didn't find that before). I may run an additional wire with the RG12 and connect it to the ground on the IEC plug.

[PRR]

> told me that if I left the transformer plugged in it would burn up.

There's a big transformer on the pole in the street, powers my house and the guy across the street. Powered-up 24/6.99 (two outages this year). Been there 20+ years. Others are pushing 40 years. Mine hasn't burned up yet. Very old ones typically (and rarely) burn on a very hot day when the power company has not allowed for increased use of A/C, not from idle or light-load.

There's a 24V transformer in my furnace, keeps the thermostat "alive" so the heat will come on when needed. That one is only a year old, but the one before was 17 years and working fine when removed (firebox rot). One in my last house was over 25 years.

My Palm Pilot charger is a transformer and I just realized it is going on 15 years non-stop. Until recently all answering machines used wall transformers powered-up all the time.

With very few exceptions, 120V transformers SHOULD be fine powered-up all the time, for the "life of the device".

They won't live forever. All insulation eventually breaks down. They typically out-live the device they power (my Palm is way past retirement age; answering machines die of lightning or get replaced by a telco answering service). But I have had PTs fail, and worst-case is they fail low-R and burn up, or zero-R and burn the line cord. A flame-resistant box and a primary fuse are wise precautions (unless you know there is a Thermal Cutout inside).