New Hitachi TRK-8600E project, line in issue

[Touchstone64]

Hi folks! My first post

First off, thanks so much for all the resources here at Boomboxery - I’ve managed to find the schematics I need to try my first repair project, a not-in-great-shape TRK-8600E.

I saved up for ages for one of these back in the early 80s, it was *fantastic*. My aim is to restore this one I found on eBay back to health, but if I can only get the line in and amp working that’ll do.

First time I powered it up, awful mono noise, virtually no volume control etc. Following the advice from these forums, a little PRF 7-78 on the control board (volume, balance, bass, treble) and the 'function' switch (source), and I now have good, clean stereo sound from the FM tuner.

The cassette unit is borked, that'll take a few band and washer replacements I expect, but the main head-scratcher I have is that, feeding a line-in signal with line in (not phono) selected on the side of the unit, with volume at 50% I can *just* hear some audio that matches what I'm playing, but it's really quiet and almost no dynamic range. (I should add there's also some horrible clipping when the source audio has any significant loudness.)

Can anyone suggest where I should start with that circuit? Any quick wins for cleaning/repairing?

I might bypass the connectors first in case they're so filthy there's almost no signal.

Thanks for any advice!!

 

[Hisrudeness]

To play an external source on this particular box you can either use an FM transmitter.Alternativlely turn the switch back over to phono and use an attenuator like the one pictured. I’ve got a couple of 8600E’s and this is the best way to play smoothly from your mobile device. The attenuators are hard to find nowadays but if you send member Reli a PM he might have a similar device.

 

[Touchstone64]

Thanks @Hisrudeness, I believe we're thinking along the same lines as it's the LINE IN connections (RCA phono plugs) I'm trying to get working. Audio is virtually non-existent with the LINE IN/PHONO switch in either position, although you can hear additional gain in the PHONO position, so something getting through the pre-amp.

Great to hear you have a couple of working 8600E's — did you have any issues with their PHONO AMP boards? Do you know of any common problems they've suffered from?

 

[AE_Stereo]

Thanks @Hisrudeness, I believe we're thinking along the same lines as it's the LINE IN connections (RCA phono plugs) I'm trying to get working. Audio is virtually non-existent with the LINE IN/PHONO switch in either position, although you can hear additional gain in the PHONO position, so something getting through the pre-amp.

Did you try keeping Record on at the same time? Try Pause + Rec + Play engaged at the same time.
In the early 70's boxes, Line-in was only for Recording!

 

[Hisrudeness]

Thanks @Hisrudeness, I believe we're thinking along the same lines as it's the LINE IN connections (RCA phono plugs) I'm trying to get working. Audio is virtually non-existent with the LINE IN/PHONO switch in either position, although you can hear additional gain in the PHONO position, so something getting through the pre-amp.

Great to hear you have a couple of working 8600E's — did you have any issues with their PHONO AMP boards? Do you know of any common problems they've suffered from?

I had no problems with the RCA’s because I use the attenuator. The only problem I’ve had with this model really is bad volume pots that have needed replacing. Other than that they‘re quite a robust box.

p.s I also have the JDM Perdisco versions.

 

[Touchstone64]

@AE_Stereo and @Hisrudeness, thanks for your patience! I'd completely forgotten about using LINE IN for recording only, doh! I guess forty years will do that to you. Right, time to experiment!

 

[Touchstone64]

So, a Monacor LPC-1 has been ordered, available on Amazon but cheaper elsewhere. I'll report my findings when it arrives

 

[Touchstone64]

Did you try keeping Record on at the same time? Try Pause + Rec + Play engaged at the same time.

(Unfortunately I can't try this as there's no response to any cassette unit controls; maybe no power. I'll start a new thread for that one!)

 

[Hisrudeness]

So, a Monacor LPC-1 has been ordered, available on Amazon but cheaper elsewhere. I'll report my findings when it arrives

will this adjust the phono signal strength or is it just an adapte?

 

[Wes125]

i like the look of these 8600's..nice box

 

[Wes125]

So, a Monacor LPC-1 has been ordered, available on Amazon but cheaper elsewhere. I'll report my findings when it arrives

if you look in the library section of this forum you will find the service manual for your trk 8600

 

[Touchstone64]

will this adjust the phono signal strength or is it just an adapte?

Good point! The output impedance is about 1% of the input so my (rudimentary) electronics knowledge suggests it's attenuating the signal. Hope I'm remembering it right...

 

[Touchstone64]

if you look in the library section of this forum you will find the service manual for your trk 8600

Indeed! As in my original post a big thank you to the members uploading and maintaining that library. Priceless!

 

[Hisrudeness]

Good point! The output impedance is about 1% of the input so my (rudimentary) electronics knowledge suggests it's attenuating the signal. Hope I'm remembering it right...

This is a video of a other one I sold last year that is using an attenuator to play from an ipad. It really smooths out the sound.

 

[Touchstone64]

This is a video of a other one I sold last year <snip>

That's a good-looking '8600! I think I might end up connecting an Airplay receiver of some kind to the attenuator, then I can Roon to it along with everything else

 

[AE_Stereo]

(Unfortunately I can't try this as there's no response to any cassette unit controls; maybe no power. I'll start a new thread for that one!)

From the Operation Manual, I infer that Line-In/Phono monitoring is only possible while Recording.

 

[Touchstone64]

From the Operation Manual, I infer that Line-In/Phono monitoring is only possible while Recording.

Oh blimey, I hope not. I have the service manual and schematics for the '8600E, but not the Operation Manual. Is it available to the public @AE_Stereo?

Reviewing the video @Hisrudeness linked in post #14 it looks like the unit's not in record mode while monitoring PHONO, but I'm only inferring that from the state of the cassette deck LEDs and button position(s). @Hisrudeness might you be able to comment?

 

[Hisrudeness]

Oh blimey, I hope not. I have the service manual and schematics for the '8600E, but not the Operation Manual. Is it available to the public @AE_Stereo?

Reviewing the video @Hisrudeness linked in post #14 it looks like the unit's not in record mode while monitoring PHONO, but I'm only inferring that from the state of the cassette deck LEDs and button position(s). @Hisrudeness might you be able to comment?

Yes, just use the attenuator on the ‘phono’ setting. No need to play/rec.

 

[Touchstone64]

So, the Monacor LPC-1 attenuator arrived five minutes ago and, I'm very happy to say, it works very well. I've hooked a Bluetooth audio receiver to the LPC-1, and the LPC-1 to the LINE IN RCA jacks with the switch in the PHONO position, and I can now play audio via the TRK-8600E via Bluetooth

I also have a spare Apple TV rev. 3 — I'll convert the digital audio to analog (from the SPDIF) and use the same attenuator trick to allow me to Airplay to the '8600 via WiFi.

Thanks so much for your advice folks!