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EICO 2036

E

estelegalize

New Member
Hi everyone,
I picked up an EICO 2036 recently (my first tube amp), and I've had a hard time sourcing material. Best I've found was a schematic (which idk how to read too well), and a catalog from 1964. Anyone have access to a service manual? I would like some literature on the unit before attempting to open it up.

I received it in working condition, but quickly realized that it has a lot of work to be done. The balance knobs make scratchy popping noises except for when its dead centered, and the bass and treble knobs work, but only on one channel each. There are 12ax7 tubes where there should be 12dw7. The rectifier is off too, it's a 5y3gt instead of a gz34. I noticed that the wires that climb over the chassis and snakes through the tubes has been rubbed down to bare wire, probably when one of the previous owners was cleaning up the unit with a wire wheel. They rubbed away all the tube markings as well, but I gathered what goes where from images of past sold units.

Anyway, any help or advice on this unit would be appreciated. Thanks.
 
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Hi, congrats on entering the world of tubes. Since that amp was sold in kit form, it would be great if you could get an assembly manual. I know it might be difficult to find but might also turn up, for instance, with a 2036 being sold on eBay. Save a search.

In the mean time, clean all controls and switches with Deoxit, replace all bad wires, see about getting some 12DW7 tubes. The 12AX7s in that spot will work (same pinout) but have higher gain in one of the two triodes in each bottle. And you’ll need a 5AR4.

You’ll eventually want to update the filter capacitors and some or all of the coupling caps. By then you will be stuck down the rabbit hole like the rest of us, never to be seen again until we post on AK.
 
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RWood said:
Hi, congrats on entering the world of tubes. Since that amp was sold in kit form, it would be great if you could get an assembly manual. I know it might be difficult to find but might also turn up, for instance, with a 2036 being sold on eBay. Save a search.

In the mean time, clean all controls and switches with Deoxit, replace all bad wires, see about getting some 12DW7 tubes. The 12AX7s in that spot will work (same pinout) but have higher gain in one of the two triodes in each bottle. And you’ll need a 5AR4.

You’ll eventually want to update the filter capacitors and some or all of the coupling caps. By then you will be stuck down the rabbit hole like the rest of us, never to be seen again until we post on AK.
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Thanks for the welcoming and advice!

Does deoxit smell similar to wd40? Cuz I smell plenty of that in here already. Decided to carefully open it up. Looks original.
 

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I once had a 2036 when I was young and far less savvy. What a wonderful sounding little amplifier! I stupidly sold it in the quest for more power...still kicking myself:(
 
BuzzK said:
I sold the amp and AFAIK the owner was happy with it.

I don't have a lot to add from the original post, but I'd be happy to entertain any questions!
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Appreciate it. Do you have a service manual? If not, which components would you advise replacing with new parts?

Thanks in advance.
 
There are a total to 4 12dw7 sockets. 2 for the preamp, and 2 for power. There was a couple of 12ax7 tubes in the power sockets. I swapped them into the preamp section and swapped a couple of og eico mullard 12dw7 into the power section. The 12ax7s sound good in the preamp section. Wondering if I need to get 12dw7 replacements when they seem to be working fine. I think I may just get the right rectifier tube for now.
 
Yes, start with a new 5AR4, put in the other correct 12DW7s and clean the switches as RWood advises. Then get an assembly manual so you can check that the rest of the amp is correctly assembled and that the voltages are in range.

It would help us to advise further if you posted some pics of from below so we can help you see how well it was assembled and if there are likely to be other issues.

On my Eico ST40 I had to replace some of the small signal tube sockets, but you could start by cleaning these too with Deoxit and small dental brushes.
 
Dandy said:
Yes, start with a new 5AR4, put in the other correct 12DW7s and clean the switches as RWood advises. Then get an assembly manual so you can check that the rest of the amp is correctly assembled and that the voltages are in range.

It would help us to advise further if you posted some pics of from below so we can help you see how well it was assembled and if there are likely to be other issues.

On my Eico ST40 I had to replace some of the small signal tube sockets, but you could start by cleaning these too with Deoxit and small dental brushes.
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Cool. I posted a pic of the wiring above. Let me know if there’s issues opening and I’ll post again.
 
Sorry, I missed that pic. With the schematic, you can now check the voltages on your unit. But usual procedure is to replace the old capacitors, especially the black tubular ones marked 400V. Get ones of the same value and the same or higher voltage. I think they are 0.027uf and 0.1uf.

I've also edited my earlier post #10 to recommend an older thread which has relevant discussion and the schematic.

Ps if WD40 has been sprayed on the controls, that is all the more reason to rinse them with Deoxit!
 
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estelegalize said:
Appreciate it. Do you have a service manual? If not, which components would you advise replacing with new parts?

Wondering if I need to get 12dw7 replacements when they seem to be working fine. I think I may just get the right rectifier tube for now.

Thanks in advance.
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1. I don't have a service manual, but I do have a schematic. Voltages are listed.

2. Replace all the electrolytic and probably the coupling caps too.

3. You can replace the PECs with small circuit PCBs stuffed with higher quality parts, but that's a bit of a pain to do. Not sure if it's worth the effort, but I did it anyway.

4. Check the value of the resistors and replace any out of spec.

5. Put the right tube in the correct position. A 12DW7 consists of a 12AX7 & 12AU7 in one package, and a 12AX7 replacement is a bad idea.
 

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Thanks for the help!

I cleaned around with a contact cleaner. Connectors, terminals, sockets, switches, and pots. The pots fee a lot better. The balance pot is still giving me trouble. Only sounds good when I find the perfect dead center. Other than that, it'll snap, crackle, and pop when its off centered. Wish there was an easy way to bypass it. The a/b system and ohm selector switches don't make noise anymore.

I noticed the phono stage tubes don't light up at all. Doesn't seem to be a problem while driving a pair of speakers or headphones.

Going to get the correct rectifier and a couple of 12dw7 next. I'll try to eventually get all new tubes. JJ seems a budget friendly choice. That's half the reason I bought a vintage amp in the first place, budget.
 
After cleaning the unit, some of the rough qualities have smoothed over. The balance knob doesn’t pop anymore. But one of electrolytic caps is still the source of the cracking and popping. When I looked closely underneath, I noticed that the twist locking tabs on the can cap are not securely twisted. The can cap is loose, so I’m wondered if it’s a grounding issue causing the noise. There’s no solder on any of locking tabs to secure the ground either.
 
Also, I’m having a hard time finding an exact can cap replacement. Does it matter if some of the values are off a bit? The og can cap is a 450v 40/20/20/20uf. I found one that’s 450v 40/40/40/40uf. Would that work? Thanks in advance.
 
estelegalize said:
Thanks! Does a higher voltage affect any other caps in the circuit? And would it affect the overall performance in any way?
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Every cap bears its own load, so to speak, and should be rated for the max voltage it is likely to see. An increase from 450v to 525v for the power supply caps won't affect the performance and will add a little more safety with today's higher line voltages. So, as trainbuftony advises.
 
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