TECHNICS SU-8080 AMPLIFIER NO POWER

[nicolas25]

hello guys, yesterday i bought a technics su-8080 integrated amp for 25€. upon testing it has no power, i check all the fuses and all are ok.power supply cable wire and power switch also ok. any ideas what should i check next? thanks

 

[mbz]

Power up the amp then check for mains AC voltage at the switched outlet at the rear.

 

[mbz]

Unit has separate transformers for L&R channels, tranformers
have thermal fuses. Maybe failed power lamp/LED?

Unplug the unit, remove fuses F1 and F2, check for continuity on transformer
primary between red and brown wires, repeat for second traf. Reinstall fuses.

Check secondary transformer voltages. Measure AC voltages between pins/posts
506 & 507
506 & 505
511 & 512
512 & 510

 

[mbz]

Also check AC voltage between pins 410 & 414, repeat for 411 and 414




Check following DC voltages (black meter probe connected to chassis/GND)
Pin 501, 502, 503, 504

 

[nicolas25]

Power up the amp then check for mains AC voltage at the switched outlet at the rear.

tnx for the reply, mains is ok

 

[nicolas25]

Unit has separate transformers for L&R channels, tranformers
have thermal fuses. Maybe failed power lamp/LED?

Unplug the unit, remove fuses F1 and F2, check for continuity on transformer
primary between red and brown wires, repeat for second traf. Reinstall fuses.

Check secondary transformer voltages. Measure AC voltages between pins/posts
506 & 507
506 & 505
511 & 512
512 & 510
View attachment 1905962

thanks, i will check

 

[century tek]

Highly unlikely that both power transformers are bad. Are you sure its not just the lamps that are burned out? Have you connected any speakers to it?

 

[nicolas25]

Unit has separate transformers for L&R channels, tranformers
have thermal fuses. Maybe failed power lamp/LED?

Unplug the unit, remove fuses F1 and F2, check for continuity on transformer
primary between red and brown wires, repeat for second traf. Reinstall fuses.

Check secondary transformer voltages. Measure AC voltages between pins/posts
506 & 507
506 & 505
511 & 512
512 & 510
View attachment 1905962

i check these pins 505 & 507 = 0.0000v
506 & 505 = 0.0000v
511 & 510 = 0.0000v
512 & 510 = 0.0000v
also pins 410 & 410, 411 & 414 has 0 acv readings

Pin 501 = 0.073 vdc
Pin 502 = -0.062
Pin 503 & Pin 504 = 0.000

 

[nicolas25]

Unit has separate transformers for L&R channels, tranformers
have thermal fuses. Maybe failed power lamp/LED?

Unplug the unit, remove fuses F1 and F2, check for continuity on transformer
primary between red and brown wires, repeat for second traf. Reinstall fuses.

Check secondary transformer voltages. Measure AC voltages between pins/posts
506 & 507
506 & 505
511 & 512
512 & 510
View attachment 1905962

continuity b/w red & brown wire,
trans 1 primary = 5 ohms
secondary = 5 ohms

2nd trans primary = 5 ohms
secondary = OL

 

[nicolas25]

Highly unlikely that both power transformers are bad. Are you sure its not just the lamps that are burned out? Have you connected any speakers to it?

i tested the lamps using a power supply and all are ok

 

[mbz]

Possibly the unit has suffered a serious surge (lightning?) with
nothing meaningful on any of the 4 secondary winding (meter ok?).

Start with the easy stuff...
T2 suggests open secondary (pins 510&511).
Check continuity between 510&512, repeat for 511&512.
Expect one OL.
Also check continuity between 410&415.
T2 feeds the power lamp so no surprise no indication.

T1 is more puzzling with prim/sec continuity.
Check continuity of the other winding, between pins 411&414
I assume these pins are wire wrap posts (don't undo wire wrap).
If possible, unload the power supply and/or T1, if plug
connections then unplug at pin 507 and 505, alternatively lift
one leg or remove rectifier D501, 503, 505, 507 then recheck
AC between 505&507.

 

[nicolas25]

okay tomorrow i will check.thanks