Radio Shack Accurian Receiver, quality of amp? (pics inside)

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Replacing the main power supply filter caps today. The main reason
is I have two units and the first unit was dead silent from hiss or hum.
The second unit has always had slight hum noticeable at 6" from speaker.
The Elna caps are from an old JVC that crapped out several years
ago from bad transistors and improper heat sinking. . .even the
pros screw up once in a while.

Charged and discharged Elnas via resistors and LEDs and both
discharged about the same rate. . .should still have a few years
of life left in them. Tracon are Korean. . .not bad in itself but the
sound hollow. Will test Tracon with same circuit and see. . .will
probably open them up and check to see if they are the really
cheap units that have a small cap inside a larger shell. . .

Old Caps: Tracon 6800mF / 50V 105 C
New Caps: Elna 6800 mF / 71V 85 C

Same diameter but Tracons are about a 3/8" shorter; The cap
height is only at the metal heat sink height. Only worried about
85 C temp rating (185 Fahrenheit) instead of the 105 C (221 Fahrenheit).

I don't really think the amplifier will every get 185 F before self-destruction though. Since the Elna are 71V they should
handle the regular voltage with headroom to spare. . .they should
never self-overheat in this amp. I've run the amp hard on several
occasions and the heat sink can get quite hot but never enough
to heat the caps. . . the unit will be installed in a larger case after
the new caps are done. . .will upload pics. . .making an MP3 boom
box with some old JVC boom box speakers. . .
 
spudfrog said:
I dusted one of these off for a project I'm working on and I have an issue trying to bypass the preamp. One channel seems to work fine, will the other cuts in with the volume about 2/3 or the way up.

Any thoughts?

untitled-2.jpg


I would check with a multimeter to see if the pot tracks the two channels on the volume control ok...
 
New power supply caps installed. . .didn't change
the hum. . .now I think it might be 120Hz and not 60Hz. . .
can't really install more capacitance. . .just minor design
flaw in the amp itself. About 3" you can hear the hum. . .
depends on sensitivity of speaker. . .
 
The transformer is:
LS-A10767-PT-T Rev B
INPUT: 120VAC 60Hz (BRN-BLK)
OUTPUT: 28.7V-0-28.7V 2A (BLU-WHT-BLU)

No VA rating was given.

PARTS EXPRESS TRANSFORMERS
Avel Y236503 160VA 22V+22V Toroidal Transformer $41.60
Avel Y236652 250VA 25V+25V Toroidal Transformer $46.10
Avel Y236653 250VA 30V+30V Toroidal Transformer $46.10


Still a great deal for the transformer alone!
 
BACK IN STOCK

These units are back in stock!

I guess Radio shack just has warehouses full of these things.

Still $14.97 in Sonoma County (1 hour north of San Francisco).

Built one into a boom box by placing it between two older
speakers from an old boom box. . .will upload soon. . . very
good work I might say. . .
 
Local RS just received 8 more Accurain Receivers! Employee stated that corporate
just keeps sending them. They are selling them as low power amplifiers and telling
customers that they only to connect a source to the RCAs labeled 'output'.

Still $14.97!

Great price for transformer alone!
 
I went to various RS nearby , I asked them to check other stores
and none had any listing on these .

Maybe they use a different number these days ?

15-1937 ( AMP )
40-1462 ( Spkrs w/Amp )

I see 5 Santa Rosa stores..which one ?
I'd like to see if they can do the free ship to store ...my store .

Wayne
 
That is interesting. You could give them a call. They really must have a warehouse full of them.

Santa Rosa Radio Shacks

546-8423
527-9419
526-4571
546-7895
526-7620

Windsor
838-1648 (Had 8 shipped to them - I bought 2 more and two we left
on the floor. The rest are probably up above the shelves)

The are selling them a amps only -- just hook into the line out.

Some comments on the design. I measured no bias voltage across
R123, R124, R223, R224!!!!!

Here is the schematic for the right channel. Still working but should be close;
also an updated parts list

Accurian Amplifier
All Resistors are gold = 5%
All Resistors are 1/8W unless otherwise stated

Main Audio Board

R18 (Y,V,R,Gl) 4.7 kΩ LED Power Supply

Left,Right
1xx,2xx

Resistors
R100,200 (Gr,Br,Br,Gl) 510 Ω Input

R101,201 (Br,Bl,O,Gl) 10 kΩ Input {0.20 mV R101 : 5.8mV R201}

R103,203 (Br,Bl,R,Gl) 1.0 kΩ {828mV : 835mV}
R104,204 (Br,Bl,R,Gl) 1.0 kΩ {836mV : 830mV}
R105,205 (Br,Bl,Br,Gl) 100 Ω {83.9mV : 83.7mV}
R106,206 (Br,Bl,Br,Gl) 100 Ω {83.9mV : 83.6mV}
R107,207 (Br,Bl,Br,Gl) 100 Ω {90.4mV : 87.7mV}
R108,208 (Br,Bl,Br,Gl) 100 Ω {85.5mV : 86.6mV}

R109,209 (Gy,R,R,Gl) 8.2 kΩ [1/4W] {13.99V}
R110,210 (Gy,R,R,Gl) 8.2 kΩ [1/4W] {13.80V}
R111,211 (Y,V,Bl,Gl) 47 Ω {41.8mV : 40.8mV}
R112,212 (Y,V,Bl,Gl) 47 Ω {39.7mV : 40.1mV}
R113,213 (Gr,Bu,R,Gl) 5.6 kΩ {2.9mV : 3.3mV} [Local Feedback?]
R114,214 (Br,Bl,R,Gl) 1.0 kΩ
R115,215 (Y,V,Bl,Gl) 47 Ω {220.2mV}
R116,216 (Y,V,Bl,Gl) 47 Ω {231.6mV : 226.4mV}
R117,217 (Y,V,R,Gl) 4.7 kΩ {1.25V : 1.25V}
R118,218 (R,V,R,Gl) 2.7 kΩ {670mV : 672mV}

R119,219 (R,R,Gl,Gl) 2.2 Ω [1/4W] to base
R120,220 (R,R,Gl,Gl) 2.2 Ω [1/4W] to base

R121,221 (O,O,Br,Gl) 330 Ω [1W] {796mV : 798mV}

R122,222 (Y,V,Gl,Gl) 4.7 Ω [1W] Zobel

R123,223 (R,R,S,Gl) 0.22 Ω [2W] Output
R124,224 (R,R,S,Gl) 0.22 Ω [2W] Output

R125,225 (O,O,R,Gl) 3.3 kΩ

R126,226 (Br,Bl,O,Gl) 10 kΩ [Possible Feedback]
R127,227 (Y,V,O,Gl) 47 kΩ

Caps
C101,201 10 µF,25V Electro
C102,202 2n7J 100 Yellow Rectangle [2.7nF? 5%]
C103,203 470J 50V Silver [47pF? 5%]
C104,204 220 µF,25V Electro
C105,205 47 Disc [47pF]
C106.206 47 Disc [47pF]
C107,207 blue
C108,208 blue
C109,209 473J 1H-P Silver Rectangle [47nF? 5%]
C110,210 100nJ 100 [Yellow Rectangle Zobel 100nF? 5%]
C111,211 1.0 µF,50V Electro

Diodes
D101,201

Transistors
Q101,201 C3198 [NPN Epitaxial Silicon (TO-92)] INPUT
Q102,202 A1266 [PNP Epitaxial Planar Low Noise (TO-92)]
Q103,203 C3198 [NPN Epitaxial Silicon (TO-92)] INPUT
Q104,204 A1266 [PNP Epitaxial Planar Low Noise (TO-92)]
Q105,205 C3198 [NPN Epitaxial Silicon (TO-92)]
Q106,206 A1266 [PNP Epitaxial Planar Low Noise (TO-92)] INPUT
Q107,207 C1027 [NPN Epitaxial Silicon (TO-92L)]
Q108,208 A1023 [PNP Epitaxial Silicon (TO-92L)]
Q109,209 TIP41C [NPN Epitaxial Planar (TO-220)] Power
Q110,210 TIP42C [PNP Epitaxial Planar (TO-220)]Power
Q111,211 Heatsink (bias?)
Q112,212 C1815 [NPN Silicon Transistor (TO-92)]

Q7 Output Relay Control

PreBoard
[milli, micro, nano,pico]
C501,502 4.7microF,50V Electro
C502,504 blue
C505,506 1microF,50V Electro
C507,508 47 Disc [47pF]
C509,510 4.7microF,50V Electro
C511,512 152J Silver Rectangle, Treble [1.5 nF 5%]
C513,514 330J Silver Rectangle, Bass [33 pF 5%]
C515,516 330J Silver Rectangle, Bass
C517,518 47 Disc [47pF]
C519,520 103J Silver Rectangle [10 nF 5%]
C521,522 682K Disc [6.8 nF 10%]
C523,524 4.7microF,50V Electro

R501,502 (R,R,O,G) 22k input
R503,504 (Br,R,O,G) 12k input
R505,506 (W,Br,O,G) 91k opamp
R507,508 (Br,Gy,R,G) 1.8k Treble
R509,510 (Br,Gy,R,G) 1.8k
R511,512 (Br,Gy,O,G) 18k
R513,514 (Br,Gy,O,G) 18k
R515,516 (O,W,R,G) 3.9k
R517,518 (Br,Bl,R,G) 1.0k
R519,520 (Y,V,O,G) 47k
R521,522 (Br,Gr,Y,G) 150k
R523,524 (R,Bl,O,G) 20k


U501 4558D JRC 3265G
U502

VR1 100k Volume Stereo
VR2 100k Balance Mono
VR3 50k Bass Stereo
VR4 50k Treble Stereo
 

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Accurian Amplifier

Parts List Update

Schmatic Update

Accurian Amplifier
All Resistors are gold = 5%
All Resistors are 1/8W unless otherwise stated

Main Audio Board

R18 (Y,V,R,Gl) 4.7 kΩ LED Power Supply

Left,Right
1xx,2xx

Resistors
R100,200 (Gr,Br,Br,Gl) 510 Ω Input

R101,201 (Br,Bl,O,Gl) 10 kΩ Input {0.20 mV R101 : 5.8mV R201}

R103,203 (Br,Bl,R,Gl) 1.0 kΩ {828mV : 835mV}
R104,204 (Br,Bl,R,Gl) 1.0 kΩ {836mV : 830mV}
R105,205 (Br,Bl,Br,Gl) 100 Ω {83.9mV : 83.7mV}
R106,206 (Br,Bl,Br,Gl) 100 Ω {83.9mV : 83.6mV}
R107,207 (Br,Bl,Br,Gl) 100 Ω {90.4mV : 87.7mV}
R108,208 (Br,Bl,Br,Gl) 100 Ω {85.5mV : 86.6mV}

R109,209 (Gy,R,R,Gl) 8.2 kΩ [1/4W] {13.99V}
R110,210 (Gy,R,R,Gl) 8.2 kΩ [1/4W] {13.80V}
R111,211 (Y,V,Bl,Gl) 47 Ω {41.8mV : 40.8mV}
R112,212 (Y,V,Bl,Gl) 47 Ω {39.7mV : 40.1mV}
R113,213 (Gr,Bu,R,Gl) 5.6 kΩ {2.9mV : 3.3mV} [NFB]
R114,214 (Br,Bl,R,Gl) 1.0 kΩ [NFB]
R115,215 (Y,V,Bl,Gl) 47 Ω {220.2mV}
R116,216 (Y,V,Bl,Gl) 47 Ω {231.6mV : 226.4mV}
R117,217 (Y,V,R,Gl) 4.7 kΩ {1.25V : 1.25V}
R118,218 (R,V,R,Gl) 2.7 kΩ {670mV : 672mV}

R119,219 (R,R,Gl,Gl) 2.2 Ω [1/4W] to base
R120,220 (R,R,Gl,Gl) 2.2 Ω [1/4W] to base

R121,221 (O,O,Br,Gl) 330 Ω [1W] {796mV : 798mV}

R122,222 (Y,V,Gl,Gl) 4.7 Ω [1W] Zobel

R123,223 (R,R,S,Gl) 0.22 Ω [2W] Output
R124,224 (R,R,S,Gl) 0.22 Ω [2W] Output

R125,225 (O,O,R,Gl) 3.3 kΩ

R126,226 (Br,Bl,O,Gl) 10 kΩ
R127,227 (Y,V,O,Gl) 47 kΩ

Caps
C101,201 10 µF,25V Electro
C102,202 2n7J 100 Yellow Rectangle [2.7nF? 5%]
C103,203 470J 50V Silver [47pF? 5%]
C104,204 220 µF,25V Electro
C105,205 47 Disc [47pF]
C106.206 47 Disc [47pF]
C107,207 blue
C108,208 blue
C109,209 473J 1H-P Silver Rectangle [47nF? 5%]
C110,210 100nJ 100 [Yellow Rectangle Zobel 100nF? 5%]
C111,211 1.0 µF,50V Electro

Diodes
D101,201

Transistors
Q101,201 C3198 [NPN Epitaxial Silicon (TO-92)] INPUT
Q102,202 A1266 [PNP Epitaxial Planar Low Noise (TO-92)]
Q103,203 C3198 [NPN Epitaxial Silicon (TO-92)] INPUT
Q104,204 A1266 [PNP Epitaxial Planar Low Noise (TO-92)]
Q105,205 C3198 [NPN Epitaxial Silicon (TO-92)]
Q106,206 A1266 [PNP Epitaxial Planar Low Noise (TO-92)] INPUT
Q107,207 C1027 [NPN Epitaxial Silicon (TO-92L)]
Q108,208 A1023 [PNP Epitaxial Silicon (TO-92L)]
Q109,209 TIP41C [NPN Epitaxial Planar (TO-220)] Power
Q110,210 TIP42C [PNP Epitaxial Planar (TO-220)]Power
Q111,211 C945 [NPN (TO-92)] Heatsink
Q112,212 C1815 [NPN Silicon Transistor (TO-92)]

Q7 Output Relay Control

PreBoard
[milli, micro, nano,pico]
C501,502 4.7microF,50V Electro
C502,504 blue
C505,506 1microF,50V Electro
C507,508 47 Disc [47pF]
C509,510 4.7microF,50V Electro
C511,512 152J Silver Rectangle, Treble [1.5 nF 5%]
C513,514 330J Silver Rectangle, Bass [33 pF 5%]
C515,516 330J Silver Rectangle, Bass
C517,518 47 Disc [47pF]
C519,520 103J Silver Rectangle [10 nF 5%]
C521,522 682K Disc [6.8 nF 10%]
C523,524 4.7microF,50V Electro

R501,502 (R,R,O,G) 22k input
R503,504 (Br,R,O,G) 12k input
R505,506 (W,Br,O,G) 91k opamp
R507,508 (Br,Gy,R,G) 1.8k Treble
R509,510 (Br,Gy,R,G) 1.8k
R511,512 (Br,Gy,O,G) 18k
R513,514 (Br,Gy,O,G) 18k
R515,516 (O,W,R,G) 3.9k
R517,518 (Br,Bl,R,G) 1.0k
R519,520 (Y,V,O,G) 47k
R521,522 (Br,Gr,Y,G) 150k
R523,524 (R,Bl,O,G) 20k


U501 4558D JRC 3265G
U502

VR1 100k Volume Stereo
VR2 100k Balance Mono
VR3 50k Bass Stereo
VR4 50k Treble Stereo
 

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Chris.... do you have the original Radio Shack schematic

This one seems strange to me.

Can you send me the original one?... this one you have posted was not made into the standard way...so it is confused to my old brain.... old fellow wants to see negative input in other side... VBE multiplier into the middle...drivers at output transistor left side...those things...input left..output rigth side..positive up and negative down..nothing under negative or upper positive and nothing after the output connector.

heheheheh

panzertoo@yahoo.com

regards,

Carlos
 
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