Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on October 17, 2022, 10:03:45 pm

Title: Matchless bulbs?
Post by: joesatch on October 17, 2022, 10:03:45 pm

what's the purpose of these bulbs in the chassis?

Title: Re: Matchless bulbs?
Post by: Latole on October 18, 2022, 03:26:35 am

Did you see the illuminated logo or front panel  ?


Google ;Matchless illuminated face plate.

https://www.matchlessamplifiers.com/support
_____________
 FAQ
How do I replace the logo lightbulbs?

There are four lamps used to illuminate the logo.

If the logo appears unevenly lit one of these lamps is probably out. The lamps are located in a reflector assembly known as a light box.

The light box is positioned just above the speaker(s) and is removed by removing the securing screws and disconnecting the two wires that supply power from the chassis.

The wires are connected with quick disconnect spades. Use a long screwdriver for easy access to the screws. If the amplifier is configured as a head, the chassis must be removed first.

*Do not attempt to go through the logo.*

_____________
How do I replace the control panel lightbulbs?


There are five lamps used to illuminate the front panel of the amplifier.

When one of these lamps requires replacement, the entire chassis must be removed from the cabinet.

To do this, first remove the power cord from the amplifier.

Then remove the back panel by loosening the hold-down screws.

Remove the two wires that provide power to the logo. These are pull-off connectors.

If the amplifier is a combo, disconnect the speaker plug located next to the fuse holder.

Carefully remove the four screws on the top of the cabinet while supporting the weight of the chassis with one hand. Slide the chassis out to replace the bulbs.

To re-install the chassis, simply reverse the process.

Title: Re: Matchless bulbs?
Post by: joesatch on October 18, 2022, 06:18:59 am

for the logo?  that's nuts

Title: Re: Matchless bulbs?
Post by: Latole on October 18, 2022, 06:23:00 am

Does this answer your question ?

Title: Re: Matchless bulbs?
Post by: shooter on October 18, 2022, 08:20:35 am

curtesy lights for working under the hood?
chassis warmer for even heating?
where do the wires lead, someone had a design to use incandescent bulbs as a "bias select" for an SE biased amp.  The less lights, the hotter it's biased

Title: Re: Matchless bulbs?
Post by: bmccowan on October 18, 2022, 09:10:21 am

It's a Matchless - expect things to be different.

Title: Re: Matchless bulbs?
Post by: joesatch on October 18, 2022, 01:25:23 pm

i am willing to bet they do more than illuminate the front panel (that reason is probably a diversion). They might reduce interference as the bulbs provide a circuit around the chassis which could block EMI

Title: Re: Matchless bulbs?
Post by: sluckey on October 18, 2022, 01:34:24 pm

Quote from: joesatch on October 18, 2022, 01:25:23 pm

i am willing to bet they do more than illuminate the front panel (that reason is probably a diversion). They might reduce interference as the bulbs provide a circuit around the chassis which could block EMI

Another quotable quote. Good one!    :l2:

Title: Re: Matchless bulbs?
Post by: SILVERGUN on October 18, 2022, 01:56:42 pm

Quote from: joesatch on October 18, 2022, 01:25:23 pm

i am willing to bet they do more than illuminate the front panel

Yeah, they help justify the price of the amp

Title: Re: Matchless bulbs?
Post by: RadioComm on October 18, 2022, 01:57:27 pm

I inherited my Father-in-Law's late 60's stereo receiver. Highbred receiver with tube preamp and transistor power amp. It also has a rail of #47 light bulbs to provide the back light to the radio dial panel.

Title: Re: Matchless bulbs?
Post by: Latole on October 18, 2022, 01:58:35 pm

Quote from: RadioComm on October 18, 2022, 01:57:27 pm

I inherited my Father-in-Law's late 60's stereo receiver. Highbred receiver with tube preamp and transistor power amp. It also had a rail of #47 light bulbs to provide the back light to the radio dial panel.

It is very common .

Title: Re: Matchless bulbs?
Post by: dwinstonwood on October 18, 2022, 02:08:23 pm

I sort of think they're installed upside down. In order to illuminate the Matchless logo, the bulbs need to be under/outside the chassis.

Title: Re: Matchless bulbs?
Post by: Latole on October 18, 2022, 02:42:44 pm

Reply 1 :  Answer from Matchless;

There are five lamps used to illuminate the front panel of the amplifier.

Title: Re: Matchless bulbs?
Post by: HotBluePlates on October 22, 2022, 07:57:17 am

Quote from: joesatch on October 18, 2022, 01:25:23 pm

i am willing to bet they do more than illuminate the front panel ...

No, they light up the front panel.  The panel was black-over-clear IIRC, was engraved through the black to leave the clear.  Then lightbulbs sprinkled through the chassis would turn on when the power switch is thrown, and light up the engraved legend on the panel.



I went Ampeg's route making a light-up faceplate: engrave the acrylic, then light from the edge.
I have a reverse-engraved panel (engraved side against the chassis), then put a few blue LEDs against the right edge.  The light transmits through the clear acrylic then is bent out to the viewer's position at the engraving.  The amp I used it on is noted here (https://el34world.com/Forum/index.php?topic=14263.msg134514#msg134514).

The photo is from a phone camera, and the LEDs tend to overdrive the sensor.  In person, it's a more subdued blue, and not as bright/intense.  I could add LEDs to the other side of the panel & tinker the dropping resistor to the LEDs to tune the brightness & balance, but just haven't bothered.

(https://i.imgur.com/5W2SnWX.jpg)

Title: Re: Matchless bulbs?
Post by: Latole on October 22, 2022, 08:16:35 am

Quote from: joesatch on October 18, 2022, 01:25:23 pm

  They might reduce interference as the bulbs provide a circuit around the chassis which could block EMI

Almost( if not all )  no amps use that bulb and there are no EMI

Title: Re: Matchless bulbs?
Post by: 66Strat on October 22, 2022, 10:25:03 am

Back lit control panel = mo mojo = mo money :icon_biggrin: