Amplifier lamp replacement

D

Dave.H

Guest
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture: http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
 
"Dave.H" <the1930s@googlemail.com> wrote in message
news:2daeb804-daea-4afb-9477-44d42d980656@w1g2000prk.googlegroups.com...
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture: http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
Click to expand...
From your picture I cannot see enough about the meters to answer you.
If there is seam or obvious means to open the case I would try to replace
the lamps.
By the looks of the circuitry, if a lamp burned out in that time period I
would suspect a tech would replace the meter, but I could be wrong.

Tom
 
On 27 Nov, 20:05, "Tom Biasi" <tombi...@optonline.net> wrote:
"Dave.H" <the19...@googlemail.com> wrote in message

news:2daeb804-daea-4afb-9477-44d42d980656@w1g2000prk.googlegroups.com...

I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia

From your picture I cannot see enough about the meters to answer you.
If there is  seam or obvious means to open the case I would try to replace
the lamps.
By the looks of the circuitry, if a lamp burned out in that time period I
would suspect a tech would replace the meter, but I could be wrong.

Tom
Click to expand...
I haven't pulled the meter out to inspect it, will do it tomorrow and
take some more pictures and link them here.

Dave
Australia
 
Dave.H wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture: http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
Drill(or melt with solder iron) 1 or 2 holes in the sides of
Click to expand...
the VU meters, then glue white LEDS in the holes.
Keep the current in the LEDS at 30-50 %, and they last forever.
I have done that in my radio, where the tuning senselights burned out.
 
"Dave.H" wrote:

I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture: http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786
Click to expand...
That style of meter is often held together at some point with sticky tape.
Remove and check.

Graham
 
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
Click to expand...

Upon closer inspection, I found that the lamps simply popped out of
the meter's side, the bulbs are about twice the side of a grain of
wheat bulb. I replaced it with a clear incandescent bulb.

Dave
Australia
 
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
Click to expand...
How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.

Dave
Australia
 
On 2008-11-28, Dave.H <the1930s@googlemail.com> wrote:
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia

How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.

Dave
Australia
Click to expand...
80W in 40W out, sounds pretty good for class AB.
 
"Dave.H" wrote:

On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.
Click to expand...
Bon't expect a waggly meter to help you !

Graham
 
Eeyore wrote:
"Dave.H" wrote:

On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786
How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.

Bon't expect a waggly meter to help you !
Click to expand...
Why not? That's how I did it when I was a kid, before I had a scope. But
first you have to make a dummy load, some humongous 8ohm resistors.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia
Click to expand...
Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.

http://picasaweb.google.com.au/the1930s/Misc#5273918283296451042
 
Joerg wrote:

Eeyore wrote:
"Dave.H" wrote:
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786
How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.

Bon't expect a waggly meter to help you !

Why not? That's how I did it when I was a kid, before I had a scope. But
first you have to make a dummy load, some humongous 8ohm resistors
Click to expand...
On music, mechanical meters tend to under-read the actual power since they can't
repond to peaks very well. They'll give an idea of average power but not peak
(which tells if your amp is being overdriven).

Graham
 
"Dave.H" wrote:

Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them.
Click to expand...
Glued ? Do they solder to anything ?


These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
Click to expand...
Bizarre.

Graham
 
On Fri, 28 Nov 2008 19:44:34 -0800 (PST), "Dave.H"
<the1930s@googlemail.com> wrote:

On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia

Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.
Click to expand...
---
I'd guess that what's glued onto the transistors are diodes and that
they're being used as temperature sensors.

JF
 
John Fields wrote:

"Dave.H" <the1930s@googlemail.com> wrote:

Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.
---
I'd guess that what's glued onto the transistors are diodes and that
they're being used as temperature sensors.
Click to expand...
For bias temperature compensation. That makes sense.

Graham
 
Dave.H wrote:

On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:

I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia


Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.

http://picasaweb.google.com.au/the1930s/Misc#5273918283296451042
Click to expand...
Thermo protection diode..


http://webpages.charter.net/jamie_5"
 
Eeyore wrote:
Joerg wrote:

Eeyore wrote:
"Dave.H" wrote:
On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:
I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786
How do I check the output power of this amp? There is no indication
anywhere as to what the power output is. It runs fine on a pair of
modern Pioneer 20w speakers, but I'd still like to know the output.,
The power input is 85w max at 240v if that helps.
Bon't expect a waggly meter to help you !
Why not? That's how I did it when I was a kid, before I had a scope. But
first you have to make a dummy load, some humongous 8ohm resistors

On music, mechanical meters tend to under-read the actual power since they can't
repond to peaks very well. They'll give an idea of average power but not peak
(which tells if your amp is being overdriven).
Click to expand...
Old trick: Feed it with a few hundred Hertz or if too lazy to build an
oscillator 50/60Hz from a doorbell transformer. Additional hi-Z
resistive divider across the output so you can listen with headphones
without blowing your ear drums out. Crank up until distortion is heard
-> read meter -> place dummy load on back porch to cool off -> done.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
Eeyore wrote:
John Fields wrote:

"Dave.H" <the1930s@googlemail.com> wrote:
Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.
---
I'd guess that what's glued onto the transistors are diodes and that
they're being used as temperature sensors.

For bias temperature compensation. That makes sense.
Click to expand...
Often they are directly in the bias circuit so it tracks with
temperature changes (somewhat), no loop.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
 
Eeyore wrote:
"Dave.H" wrote:

Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them.

Glued ? Do they solder to anything ?


These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?

Bizarre.

Graham

Temperature sensor,to stop over heating.
Click to expand...
 
Dave.H wrote:
On 30 Nov, 03:03, John Fields <jfie...@austininstruments.com> wrote:

On Fri, 28 Nov 2008 19:44:34 -0800 (PST), "Dave.H"



the19...@googlemail.com> wrote:

On 27 Nov, 12:50, "Dave.H" <the19...@googlemail.com> wrote:

I have an old stereo amplifier in whch some of the indicator lamps
have blown. Unfortunately two of these are enclosed in the VU meters,
I'm wondering if it's possible to open up the meters and replace them,
if not, hot glue some replacements to the exterior.

Picture:http://picasaweb.google.com.au/the1930s/Misc#5273147456088310786

TIA

Dave
Australia

Another question I have about this amp. There are four (output)
transistor mounted on a large heatsink at the rear of the chassis, two
of these have two core wires glued on to them. These wires are
soldered in holes on the PC board that have the diode ( >| ) symbol.
What are the purpose of these wires?
I have the schematic that is glued to the bottom of the unit, I can
remove the bottom and scan it if it helps.

---
I'd guess that what's glued onto the transistors are diodes and that
they're being used as temperature sensors.

JF


I think you're right. I took another, closer look under the hood of
the amp, they are not wires like I thought, but leads of a component
covered in clear insulation. And since that component is green, with a
black band, I take it to be a diode. The reason I didn't see the diode
before, was because it's covered in glue, which has dried out on one
transistor and the diode is hanging in midair. Should I just superglue
it back on, or is there a special type of glue for this?

Dave
Australia
Actually, I think they are normally hot glued on.
Click to expand...


http://webpages.charter.net/jamie_5"
 
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