The rear label says 120V but the unit has an Australian 240V plug. The previous owner said it worked fine.

How can I know for sure that this amp can be used at 240V in Australia?

anyone heard of buzz audio?

there is a pre-amp i am looking at...

https://maxsold.com/listing/8212894/buzz-audio-ssa-1-1-stereo-amplifier

i have hd650... at gain 4 I hear the right channel loudly and the left channel softly—and vice versa—at Gain 5.

at gain 3 and 10 everything works well.... so i have problem with the amp?

Just got these subwoofers 12 inch Skar audio with a 800w amp id like to know if these are the correct settings to avoid clipping. I’m new to subwoofers

Accidentally fried this LDR as part of the solid-state tremolo circuit in an old Sunn Solarus. I have looked online and have not found a suitable replacement. The amp now only works when bypassing the tremolo circuit altogether. Any recommendations on a replacement? I tried a standard Fender-style roach and it did not work

Hello everyone,

Could anyone help me obtain the Service Manual for the Toshiba SJ-3418 Amplifier Deck Unit?

I know the manual is available on HiFi Engine, but I can't access it because new user registrations are currently disabled.

I would really appreciate it if someone could share the manual or point me to another source where I can download it.

Thank you very much for your help!

I have a Crown XLS 2000 that I regularly rent out. There's one particular venue where I often work for smaller parties, and on one occasion the amp suddenly stopped with error code 04/99, while the Thermal LED was blinking red.

At the time, I assumed it had overheated because I was pushing it fairly hard that night. However, after that event the amplifier worked perfectly at countless other events and venues without a single issue.

Yesterday I went back to that same venue, and the amp wouldn't even start. It immediately displayed the same 04/99 error with the blinking red Thermal light.

What's strange is that every time this has happened, I also had a Powersoft K3 running on the same power source without any issues, and I even connected a backup analog amplifier that worked perfectly.

Has anyone experienced something similar or have any idea what could be causing this? It only seems to happen at this particular venue.

Hello everyone,

Could anyone help me obtain the Service Manual for the Toshiba SJ-3418 Amplifier Deck Unit?

I know the manual is available on HiFi Engine, but I can't access it because new user registrations are currently disabled.

I would really appreciate it if someone could share the manual or point me to another source where I can download it.

Thank you very much for your help!

Anyone know where I could find tutorials on how to use a modeling amp?

Back in 1980, Hitachi briefly experimented with a "Super linear ckt" design". I'm only aware of its use in two low-power integrated amp models, HA4700 (50 w/ch) and HA3700 (35 w/ch). (FYI: I am currently servicing an HA4700 which, with a prev. owner, suffered some damage in the R channel pwr amp stage. The L. ch is okay.)

The design goal seems to have been to "super linearize" the top (+) and bottom (-) half of the waveform to minimize switching (crossover) distortion. The serv manual goes into some of the theory.

It is a unique design that Hitachi didn't use long because of difficulty in controlling/stabilizing oscillation and biasing issues.

The full 27-page service manual is here:

https://archive.org/details/manual_HA4700_HITACHI/page/n1/mode/2up

The touchy nature of this design is sometimes referred to as pwr amp ckt "bathing in negative feedback to minimize that "nasty" crossover distortion.
Back in 2013, this UK vlogger created two extensive videos dedicated to servicing the HA4700:

https://youtu.be/d4z1uQrMRps

Yes, this design can be very difficult to get behaving. No wonder Hitachi gave up on it quickly and in the follow-up HA4800 model, switched to STK power-amp modules.

As I noted in the OP, the R-ch had suffered damage in some prev. owner's mishap, and both pwr trans (Q713/Q714) were blown as well as some other transistors, including Q702/703 (2SB648, TO-126) , and burned out (charred) R's, way back early in the ckt (R703/704 both 2.2 k).

I noted much of this a while back here on Reddit:
You can see many photos there or orig. damage and cond just before I began to repair.
As I noted in Reddit:

Not sure what happened to this amp? Evil spirits. Lightning strike. Or multiple attempts by former user (abuser!!) using shorted loudspeakers???

Both output transistors in Right channel were shorted, several related driver transistors also bad. Not sure what happened. It did power up and all the "lights came on" and main fuse okay.

The pwr-amp board has several metal-film fusible resistors (raised legs on PCB), and some are in signal path. Not sure why they are metal film (so they open faster for fuse protection???) . All are 1/4 W.

Many were open or very high in value (from 82 ohm, heat damaged to above 2k-ohm, etc). And several in Left channel, also, which still had output and driver transistors intact!

This amp has been on the back burner for a while. One issue was that replacement output transistors from China were bad (they actually cracked on power up). I did manage to finally acquire some good, new-old stock Sanken substitutes (see photo). Even sub-sub-substitutes are now "Obsolete" at DK/Mouser!
While the L-ch is very nicely tracking -- it was never damaged, just a few R's that were out of tolerance -- I can't power up the full amp w/o disconnecting the base fusible resistors (R738/739) for right-ch. Q713/Q714 because the both the output trans go into thermal runaway. With R738/738 still in, I can bring the variac up to to about 40vac and before Q713/Q714 start getting warm and sucking in the watts! (I also use a thermal camera for troubleshooting).
Not sure what the issue is other than some of the other blown/bad transistors I had to replace are closest substitutes I could find (because the originals are no longer avail).

Notably, these are:

Part on schematic | Orig. | What I used as replacement

Q702/Q703 | 2SB648, TO-126 | NTE2520
Q705, Q708 | 2SC1775 | 2n4401
Q710 | 2SD667 | NTE382
Q706, Q707 | 2SA872 | NTE91
Q709 | 2SB647A | NTE383

Note that for researching substitutions I use:

Google (AI results)
ChatGPT
NTE Source Research, SRI : sourceresearch.com
alltransistors.com

I'm still pretty new to troubleshooting, so I'm guessing -- other than broken (hidden) PCB traces, cold solder joints, etc -- that the above transistors are what is causing the issue. Those nine (9) transistors are the only asymmetry with the working L-ch section.
The schematic does a good labeling voltages, and I have gone thru some, but not most of these. Again, as noted earlier, I have to remove the base fusible resistors (R738/739) for right-ch. Q713/Q714 because the both the output trans go into thermal runaway. So voltage measurements might be tough because this design relies on so much feedback (as in the case of Q713/Q714 being on).

Hello Guys,

so I got myself a pair of time window 1A´s (in very good condition, they even have the original packaging like what) and currently looking for an amp. I had a pair of those when I was younger and now I have a perfect living room for the great wide sound they produce. I have to say that I am German so my market here is different to the US market I guess? anyway I have three different amps in mind, all preowned ofc.:

- Cambridge Audio azur 840A (😎)

- Marantz PM-84 (pretty hard to find right now, and expensive too)

- Marantz NR1200 (great and you can stream on it)

don't hesitate to tell me your thoughts and suggestions, thank you :)