Akai 4000D rest thread

[Markoneswift]

I have a nice 4000D that works well and sounds pretty good.

Having read many threads about the problematic 2sc458LG 'outhouse' transistors that my deck is sprinkled with, I decided to embark upon a little modernisation and restoration.

I have already cleaned and lapped the heads, as well as replaced the pinch roller with a good one. Most controls have been deoxited including the record switch bar.

As things are right now, I have pulled all four amp cards and replaced the electrolytic caps on one of the four boards. Unfortunately I'm forced to use radial caps, rather than original axial type, due to lack of locally available parts.

Here's an original board and the recapped one....

 

[Markoneswift]

Can I change the title ? Should be resto not rest....

 

[Jonny Ramone]

I want to do this to mine someday.

 

[Markoneswift]

I've got the two record boards recapped now, just gotta do the play boards now. Then on to the 2sc458 replacements. I'm going to need to insulate the legs of the BC550's.....

 

[MRL_Audio]

 

[Markoneswift]

You might need more popcorn, this is gonna take a while. I'm onto trying to work out how to cross-leg the replacement BC550 transistors now. I will be shielding the legs with sleeving but I hope I get the ECB the right way round......

 

[Jonny Ramone]

I thought the boards I looked at looked like plug-ins. That's cool.

 

[sol7]

You lapped your own heads? Dare I ask for a picture of them?

 

[Markoneswift]

You lapped your own heads? Dare I ask for a picture of them?

You may, but they look like sh!t lol. I don't quite know how I got onto doing it but I had a really bad buildup of crud on mine that refused to shift. I had at it with the aluminium polish as suggested somewhere here on AK and afterward it sounded WAY better. Are the heads still to original spec - I doubt it, but I haven't ruined them (yet).

 

[Markoneswift]

I thought the boards I looked at looked like plug-ins. That's cool.

Yeah it's a really nice setup. The previous Akai that I had was all hard wired so when I saw removable boards I was happy

 

[sol7]

You may, but they look like sh!t lol. I don't quite know how I got onto doing it but I had a really bad buildup of crud on mine that refused to shift. I had at it with the aluminium polish as suggested somewhere here on AK and afterward it sounded WAY better. Are the heads still to original spec - I doubt it, but I haven't ruined them (yet).

Ah... So you just polished them. Used Noxon?

 

[Markoneswift]

Ah... So you just polished them. Used Noxon?

Ah yeah I guess it was a polish, it's just that the thread I was following on the topic kept mentioning lapping so I went with it. I used some brand of aluminium polish - the one you mention isn't available here (like a lot of things).

 

[dhnash]

Head polishing, which is what you did, and head relapping are two different things. Polishing can help to remove surface contamination or corrosion. Relapping is a process intended to remove the wear pattern that develops due to the abrasive action of magnetic tape passing over the face of the head. The attached file discusses the characteristics and effects of head wear and the application of relapping in addressing these.

 

[Markoneswift]

Finished recapping and transistor swapping on the record boards. All BC550 legs insulted to avoid mishaps while Base Collector swapping !

 

[Markoneswift]

Well it's all back together and working fine. I'm quite happy about this, mainly because it's my first overhaul of a system rather than just break / fix work.

Playback channels are working nice, just need to check record now. I am actually pleased with myself for getting all the transistors swapped around the right way